Organic electroluminescent materials and devices

ABSTRACT

Imidazophenanthridine ligands and metal complexes are provided. The compounds exhibit improved stability through a linking substitution that links a nitrogen bonded carbon of an imidizole ring to a carbon on the adjacent fused aryl ring. The compounds may be used in organic light emitting devices, particularly as emissive dopants, providing devices with improved efficiency, stability, and manufacturing. In particular, the compounds provided herein may be used in blue devices having high efficiency.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation-in-part of co-pending U.S. patentapplication Ser. No. 14/933,684, filed Nov. 5, 2015, which is acontinuation-in-part of PCT application Serial No. PCT/US15/29269, filedon May 5, 2015, which claims priority to U.S. Provisional ApplicationSer. No. 61/990,239, filed on May 8, 2014, and to U.S. ProvisionalApplication Ser. No. 62/082,970, filed on Nov. 21, 2014, the entirecontents of which are incorporated herein by reference.

FIELD OF THE INVENTION

The present invention generally relates to novel compounds, compositionscomprising the same, and applications of the compounds and compositions,including organic electroluminescent devices comprising the compoundsand/or compositions.

BACKGROUND OF THE INVENTION

Generally, an OLED comprises at least one organic layer disposed betweenand electrically connected to an anode and a cathode. When a current isapplied, the anode injects holes and the cathode injects electrons intothe organic layer(s). The injected holes and electrons each migratetoward the oppositely charged electrode. When an electron and holelocalize on the same molecule, an “exciton,” which is a localizedelectron-hole pair having an excited energy state, is formed. Light isemitted when the exciton relaxes via a photoemissive mechanism. In somecases, the exciton may be localized on an excimer or an exciplex.Non-radiative mechanisms, such as thermal relaxation, may also occur,but are generally considered undesirable.

The initial OLEDs used emissive molecules that emitted light from theirsinglet states (“fluorescence”) as disclosed, for example, in U.S. Pat.No. 4,769,292, which is incorporated by reference in its entirety.Fluorescent emission generally occurs in a time frame of less than 10nanoseconds.

More recently, OLEDs having emissive materials that emit light fromtriplet states (“phosphorescence”) have been demonstrated. Baldo et al.,“Highly Efficient Phosphorescent Emission from OrganicElectroluminescent Devices,” Nature, vol. 395, 151-154, 1998;(“Baldo-I”) and Baldo et al., “Very high-efficiency green organiclight-emitting devices based on electrophosphorescence,” Appl. Phys.Lett., vol. 75, No. 3, 4-6 (1999) (“Baldo-II”), which are incorporatedby reference in their entireties. Phosphorescence may be referred to asa “forbidden” transition because the transition requires a change inspin states, and quantum mechanics indicates that such a transition isnot favored. As a result, phosphorescence generally occurs in a timeframe exceeding at least 10 nanoseconds, and typically greater than 100nanoseconds. If the natural radiative lifetime of phosphorescence is toolong, triplets may decay by a non-radiative mechanism, such that nolight is emitted. Organic phosphorescence is also often observed inmolecules containing heteroatoms with unshared pairs of electrons atvery low temperatures. 2,2′-bipyridine is such a molecule. Non-radiativedecay mechanisms are typically temperature dependent, such that anorganic material that exhibits phosphorescence at liquid nitrogentemperatures typically does not exhibit phosphorescence at roomtemperature. But, as demonstrated by Baldo, this problem may beaddressed by selecting phosphorescent compounds that do phosphoresce atroom temperature. Representative emissive layers include doped orun-doped phosphorescent organometallic materials such as disclosed inU.S. Pat. Nos. 6,303,238; 6,310,360; 6,830,828 and 6,835,469; U.S.Patent Application Publication No. 2002-0182441; and WO 2002/074015.

Phosphorescence may be preceded by a transition from a triplet excitedstate to an intermediate non-triplet state from which the emissive decayoccurs. For example, organic molecules coordinated to lanthanideelements often phosphoresce from excited states localized on thelanthanide metal. However, such materials do not phosphoresce directlyfrom a triplet excited state but instead emit from an atomic excitedstate centered on the lanthanide metal ion. The europium diketonatecomplexes illustrate one group of these types of species.

Phosphorescence from triplets can be enhanced over fluorescence byconfining, preferably through bonding, the organic molecule in closeproximity to an atom of high atomic number. This phenomenon, called theheavy atom effect, is created by a mechanism known as spin-orbitcoupling. Such a phosphorescent transition may be observed from anexcited metal-to-ligand charge transfer (MLCT) state of anorganometallic molecule such as tris(2-phenylpyridine)iridium(III).

Opto-electronic devices that make use of organic materials are becomingincreasingly desirable for a number of reasons. Many of the materialsused to make such devices are relatively inexpensive, so organicopto-electronic devices have the potential for cost advantages overinorganic devices. In addition, the inherent properties of organicmaterials, such as their flexibility, may make them well suited forparticular applications such as fabrication on a flexible substrate.Examples of organic opto-electronic devices include organic lightemitting devices (OLEDs), organic phototransistors, organic photovoltaiccells, and organic photodetectors. For OLEDs, the organic materials mayhave performance advantages over conventional materials. For example,the wavelength at which an organic emissive layer emits light maygenerally be readily tuned with appropriate dopants.

OLEDs make use of thin organic films that emit light when voltage isapplied across the device. OLEDs are becoming an increasinglyinteresting technology for use in applications such as flat paneldisplays, illumination, and backlighting. Several OLED materials andconfigurations are described in U.S. Pat. Nos. 5,844,363; 6,303,238; and5,707,745, which are incorporated herein by reference in their entirety.

One application for phosphorescent emissive molecules is a full colordisplay. Industry standards for such a display call for pixels adaptedto emit particular colors, referred to as “saturated” colors. Inparticular, these standards call for saturated red, green, and bluepixels. Alternatively, the OLED can be designed to emit white light. Inconventional liquid crystal displays, emission from a white backlight isfiltered using absorption filters to produce red, green and blueemission. The same technique can also be used with OLEDs. The white OLEDcan be either a single EML device or a stacked structure. Color may bemeasured using CIE coordinates, which are well known to the art.

One example of a green emissive molecule is tris(2-phenylpyridine)iridium, denoted Ir(ppy)₃, which has the following structure:

In this, and later figures herein, we depict the dative bond fromnitrogen to metal (here, Ir) as a straight line.

As used herein, the term “organic” includes polymeric materials as wellas small molecule organic materials that may be used to fabricateorganic opto-electronic devices. “Small molecule” refers to any organicmaterial that is not a polymer, and “small molecules” may actually bequite large. Small molecules may include repeat units in somecircumstances. For example, using a long chain alkyl group as asubstituent does not remove a molecule from the “small molecule” class.Small molecules may also be incorporated into polymers, for example as apendent group on a polymer backbone or as a part of the backbone. Smallmolecules may also serve as the core moiety of a dendrimer, whichconsists of a series of chemical shells built on the core moiety. Thecore moiety of a dendrimer may be a fluorescent or phosphorescent smallmolecule emitter. A dendrimer may be a “small molecule,” and it isbelieved that all dendrimers currently used in the field of OLEDs aresmall molecules.

As used herein, “top” means furthest away from the substrate, while“bottom” means closest to the substrate. Where a first layer isdescribed as “disposed over” a second layer, the first layer is disposedfurther away from substrate. There may be other layers between the firstand second layer, unless it is specified that the first layer is “incontact with” the second layer. For example, a cathode may be describedas “disposed over” an anode, even though there are various organiclayers in between.

As used herein, “solution processible” means capable of being dissolved,dispersed, or transported in and/or deposited from a liquid medium,either in solution or suspension form.

A ligand may be referred to as “photoactive” when it is believed thatthe ligand directly contributes to the photoactive properties of anemissive material. A ligand may be referred to as “ancillary” when it isbelieved that the ligand does not contribute to the photoactiveproperties of an emissive material, although an ancillary ligand mayalter the properties of a photoactive ligand.

As used herein, and as would be generally understood by one skilled inthe art, a first “Highest Occupied Molecular Orbital” (HOMO) or “LowestUnoccupied Molecular Orbital” (LUMO) energy level is “greater than” or“higher than” a second HOMO or LUMO energy level if the first energylevel is closer to the vacuum energy level. Since ionization potentials(IP) are measured as a negative energy relative to a vacuum level, ahigher HOMO energy level corresponds to an IP having a smaller absolutevalue (an IP that is less negative). Similarly, a higher LUMO energylevel corresponds to an electron affinity (EA) having a smaller absolutevalue (an EA that is less negative). On a conventional energy leveldiagram, with the vacuum level at the top, the LUMO energy level of amaterial is higher than the HOMO energy level of the same material. A“higher” HOMO or LUMO energy level appears closer to the top of such adiagram than a “lower” HOMO or LUMO energy level.

As used herein, and as would be generally understood by one skilled inthe art, a first work function is “greater than” or “higher than” asecond work function if the first work function has a higher absolutevalue. Because work functions are generally measured as negative numbersrelative to vacuum level, this means that a “higher” work function ismore negative. On a conventional energy level diagram, with the vacuumlevel at the top, a “higher” work function is illustrated as furtheraway from the vacuum level in the downward direction. Thus, thedefinitions of HOMO and LUMO energy levels follow a different conventionthan work functions.

More details on OLEDs, and the definitions described above, can be foundin U.S. Pat. No. 7,279,704, which is incorporated herein by reference inits entirety.

SUMMARY OF THE INVENTION

According to an aspect of the present disclosure, a compound having astructure (L_(A))_(n)ML_(m) according to Formula 1,

is disclosed. In Formula 1, M is a metal having an atomic weight greaterthan 40, n has a value of at least 1 and m+n is the maximum number ofligands that may be attached to the metal;wherein A is a linking group selected from the group consisting of A1thorough A222 shown below; wherein any one of the ring atoms to whichR^(1b) to R^(1g) are attached may be replaced with a nitrogen atom,wherein when the ring atom is replaced with a nitrogen atom thecorresponding R group is not present; andwherein L is a substituted or unsubstituted cyclometallated ligand;wherein R^(1b) is selected from the group consisting of:

wherein R^(1b) is selected from the group consisting of:

wherein R^(1c) is selected from the group consisting of:

wherein R^(1d) is selected from the group consisting of:

wherein R^(1e) is selected from the group consisting of:

wherein R^(1f) is selected from the group consisting of:

wherein which R^(1g)=H;wherein the structures A1 through A222 are:

According to another aspect of the present disclosure, an organic lightemitting device is disclosed. The OLED comprises an anode; a cathode;and an organic layer disposed between the anode and the cathode, whereinthe organic layer comprises the compound having the structure accordingto Formula 1.

According to another aspect of the present disclosure, a formulationcomprising the compound having the structure according to Formula 1 isalso disclosed.

BRIEF DESCRIPTION OF THE DRAWINGS

The foregoing summary, as well as the following detailed description ofexemplary embodiments of the compounds, compositions and devices inaccordance with the present invention, will be better understood whenread in conjunction with the appended drawings of exemplary embodiments.It should be understood, however, that the invention is not limited tothe precise arrangements and instrumentalities shown.

In the drawings:

FIG. 1 shows an exemplary organic light emitting device 100; and

FIG. 2 illustrates an exemplary organic light emitting device 200according to the present disclosure.

FIGS. 3a and 3b illustrate a computational model of minimizedbond-broken geometry (top) and minimized non-bond broken geometry(bottom) for comparative example 1.

FIG. 4 illustrates a MALDI negative mode mass spectrum for comparativecompound 4. The highest intensity peak corresponds to fragmentation ofthe imidazole ring.

FIG. 5 illustrates the x-ray crystal structure of3,4-dihydrodibenzo[b,ij]imidazo[2,1,5-de]quinolizine.

FIG. 6 illustrates the x-ray crystal structure of3,3-dimethyl-3,4-dihydro-1,2a1-diaza-3-silabenzo[fg]aceanthrylene.

FIG. 7 depicts Emission spectrum of Compound 49 in 77 K and roomtemperature 2-methyl THF solvent and solid state PMMA matrix.

DETAILED DESCRIPTION

Generally, an OLED comprises at least one organic layer disposed betweenand electrically connected to an anode and a cathode. When a current isapplied, the anode injects holes and the cathode injects electrons intothe organic layer(s). The injected holes and electrons each migratetoward the oppositely charged electrode. When an electron and holelocalize on the same molecule, an “exciton,” which is a localizedelectron-hole pair having an excited energy state, is formed. Light isemitted when the exciton relaxes via a photoemissive mechanism. In somecases, the exciton may be localized on an excimer or an exciplex.Non-radiative mechanisms, such as thermal relaxation, may also occur,but are generally considered undesirable.

The initial OLEDs used emissive molecules that emitted light from theirsinglet states (“fluorescence”) as disclosed, for example, in U.S. Pat.No. 4,769,292, which is incorporated by reference in its entirety.Fluorescent emission generally occurs in a time frame of less than 10nanoseconds.

More recently, OLEDs having emissive materials that emit light fromtriplet states (“phosphorescence”) have been demonstrated. Baldo et al.,“Highly Efficient Phosphorescent Emission from OrganicElectroluminescent Devices,” Nature, vol. 395, 151-154, 1998;(“Baldo-I”) and Baldo et al., “Very high-efficiency green organiclight-emitting devices based on electrophosphorescence,” Appl. Phys.Lett., vol. 75, No. 3, 4-6 (1999) (“Baldo-II”), which are incorporatedby reference in their entireties. Phosphorescence is described in moredetail in U.S. Pat. No. 7,279,704 at cols. 5-6, which are incorporatedby reference.

Imidazophenanthridines are useful ligands that can provide 460 nmemission when ligated to both platinum and iridium metals.Phosphorescent imidazophenanthridine complexes can provide deep blueemission with tunable photoluminescent quantum yield ranging from nearlyzero to unity. Unfortunately, the device lifetime is limited for bothiridium and platinum based blue-emitting complexes. We provide astrategy herein to improve the stability of the imidazophenanthridineligand by addressing a bond on the ligand that is shown by computationaltheory, mass spec fragmentation analysis, and photooxidative studies tobe a weak bond due to polycyclic ring strain and electronic structure.

FIG. 1 shows an organic light emitting device 100. The figures are notnecessarily drawn to scale. Device 100 may include a substrate 110, ananode 115, a hole injection layer 120, a hole transport layer 125, anelectron blocking layer 130, an emissive layer 135, a hole blockinglayer 140, an electron transport layer 145, an electron injection layer150, a protective layer 155, a cathode 160, and a barrier layer 170.Cathode 160 is a compound cathode having a first conductive layer 162and a second conductive layer 164. Device 100 may be fabricated bydepositing the layers described, in order. The properties and functionsof these various layers, as well as example materials, are described inmore detail in U.S. Pat. No. 7,279,704 at cols. 6-10, which areincorporated by reference.

More examples for each of these layers are available. For example, aflexible and transparent substrate-anode combination is disclosed inU.S. Pat. No. 5,844,363, which is incorporated by reference in itsentirety. An example of a p-doped hole transport layer is m-MTDATA dopedwith F₄-TCNQ at a molar ratio of 50:1, as disclosed in U.S. PatentApplication Publication No. 2003/0230980, which is incorporated byreference in its entirety. Examples of emissive and host materials aredisclosed in U.S. Pat. No. 6,303,238 to Thompson et al., which isincorporated by reference in its entirety. An example of an n-dopedelectron transport layer is BPhen doped with Li at a molar ratio of 1:1,as disclosed in U.S. Patent Application Publication No. 2003/0230980,which is incorporated by reference in its entirety. U.S. Pat. Nos.5,703,436 and 5,707,745, which are incorporated by reference in theirentireties, disclose examples of cathodes including compound cathodeshaving a thin layer of metal such as Mg:Ag with an overlyingtransparent, electrically-conductive, sputter-deposited ITO layer. Thetheory and use of blocking layers is described in more detail in U.S.Pat. No. 6,097,147 and U.S. Patent Application Publication No.2003/0230980, which are incorporated by reference in their entireties.Examples of injection layers are provided in U.S. Patent ApplicationPublication No. 2004/0174116, which is incorporated by reference in itsentirety. A description of protective layers may be found in U.S. PatentApplication Publication No. 2004/0174116, which is incorporated byreference in its entirety.

FIG. 2 shows an inverted OLED 200. The device includes a substrate 210,a cathode 215, an emissive layer 220, a hole transport layer 225, and ananode 230. Device 200 may be fabricated by depositing the layersdescribed, in order. Because the most common OLED configuration has acathode disposed over the anode, and device 200 has cathode 215 disposedunder anode 230, device 200 may be referred to as an “inverted” OLED.Materials similar to those described with respect to device 100 may beused in the corresponding layers of device 200. FIG. 2 provides oneexample of how some layers may be omitted from the structure of device100.

The simple layered structure illustrated in FIGS. 1 and 2 is provided byway of non-limiting example, and it is understood that embodiments ofthe invention may be used in connection with a wide variety of otherstructures. The specific materials and structures described areexemplary in nature, and other materials and structures may be used.Functional OLEDs may be achieved by combining the various layersdescribed in different ways, or layers may be omitted entirely, based ondesign, performance, and cost factors. Other layers not specificallydescribed may also be included. Materials other than those specificallydescribed may be used. Although many of the examples provided hereindescribe various layers as comprising a single material, it isunderstood that combinations of materials, such as a mixture of host anddopant, or more generally a mixture, may be used. Also, the layers mayhave various sublayers. The names given to the various layers herein arenot intended to be strictly limiting. For example, in device 200, holetransport layer 225 transports holes and injects holes into emissivelayer 220, and may be described as a hole transport layer or a holeinjection layer. In one embodiment, an OLED may be described as havingan “organic layer” disposed between a cathode and an anode. This organiclayer may comprise a single layer, or may further comprise multiplelayers of different organic materials as described, for example, withrespect to FIGS. 1 and 2.

Structures and materials not specifically described may also be used,such as OLEDs comprised of polymeric materials (PLEDs) such as disclosedin U.S. Pat. No. 5,247,190 to Friend et al., which is incorporated byreference in its entirety. By way of further example, OLEDs having asingle organic layer may be used. OLEDs may be stacked, for example asdescribed in U.S. Pat. No. 5,707,745 to Forrest et al, which isincorporated by reference in its entirety. The OLED structure maydeviate from the simple layered structure illustrated in FIGS. 1 and 2.For example, the substrate may include an angled reflective surface toimprove out-coupling, such as a mesa structure as described in U.S. Pat.No. 6,091,195 to Forrest et al., and/or a pit structure as described inU.S. Pat. No. 5,834,893 to Bulovic et al., which are incorporated byreference in their entireties.

Unless otherwise specified, any of the layers of the various embodimentsmay be deposited by any suitable method. For the organic layers,preferred methods include thermal evaporation, ink-jet, such asdescribed in U.S. Pat. Nos. 6,013,982 and 6,087,196, which areincorporated by reference in their entireties, organic vapor phasedeposition (OVPD), such as described in U.S. Pat. No. 6,337,102 toForrest et al., which is incorporated by reference in its entirety, anddeposition by organic vapor jet printing (OVJP), such as described inU.S. Pat. No. 7,431,968, which is incorporated by reference in itsentirety. Other suitable deposition methods include spin coating andother solution based processes. Solution based processes are preferablycarried out in nitrogen or an inert atmosphere. For the other layers,preferred methods include thermal evaporation. Preferred patterningmethods include deposition through a mask, cold welding such asdescribed in U.S. Pat. Nos. 6,294,398 and 6,468,819, which areincorporated by reference in their entireties, and patterning associatedwith some of the deposition methods such as ink-jet and OVJD. Othermethods may also be used. The materials to be deposited may be modifiedto make them compatible with a particular deposition method. Forexample, substituents such as alkyl and aryl groups, branched orunbranched, and preferably containing at least 3 carbons, may be used insmall molecules to enhance their ability to undergo solution processing.Substituents having 20 carbons or more may be used, and 3-20 carbons isa preferred range. Materials with asymmetric structures may have bettersolution processibility than those having symmetric structures, becauseasymmetric materials may have a lower tendency to recrystallize.Dendrimer substituents may be used to enhance the ability of smallmolecules to undergo solution processing.

Devices fabricated in accordance with embodiments of the presentinvention may further optionally comprise a barrier layer. One purposeof the barrier layer is to protect the electrodes and organic layersfrom damaging exposure to harmful species in the environment includingmoisture, vapor and/or gases, etc. The barrier layer may be depositedover, under or next to a substrate, an electrode, or over any otherparts of a device including an edge. The barrier layer may comprise asingle layer, or multiple layers. The barrier layer may be formed byvarious known chemical vapor deposition techniques and may includecompositions having a single phase as well as compositions havingmultiple phases. Any suitable material or combination of materials maybe used for the barrier layer. The barrier layer may incorporate aninorganic or an organic compound or both. The preferred barrier layercomprises a mixture of a polymeric material and a non-polymeric materialas described in U.S. Pat. No. 7,968,146, PCT Pat. Application Nos.PCT/US2007/023098 and PCT/US2009/042829, which are herein incorporatedby reference in their entireties. To be considered a “mixture”, theaforesaid polymeric and non-polymeric materials comprising the barrierlayer should be deposited under the same reaction conditions and/or atthe same time. The weight ratio of polymeric to non-polymeric materialmay be in the range of 95:5 to 5:95. The polymeric material and thenon-polymeric material may be created from the same precursor material.In one example, the mixture of a polymeric material and a non-polymericmaterial consists essentially of polymeric silicon and inorganicsilicon.

Devices fabricated in accordance with embodiments of the invention canbe incorporated into a wide variety of electronic component modules (orunits) that can be incorporated into a variety of electronic products orintermediate components. Examples of such electronic products orintermediate components include display screens, lighting devices suchas discrete light source devices or lighting panels, etc. that can beutilized by the end-user product manufacturers. Such electroniccomponent modules can optionally include the driving electronics and/orpower source(s). Devices fabricated in accordance with embodiments ofthe invention can be incorporated into a wide variety of consumerproducts that have one or more of the electronic component modules (orunits) incorporated therein. Such consumer products would include anykind of products that include one or more light source(s) and/or one ormore of some type of visual displays. Some examples of such consumerproducts include flat panel displays, curved displays, computermonitors, medical monitors, televisions, billboards, lights for interioror exterior illumination and/or signaling, heads-up displays, fully orpartially transparent displays, flexible displays, rollable displays,foldable displays, stretchable displays, laser printers, telephones,cell phones, tablets, phablets, personal digital assistants (PDAs),wearable devices, laptop computers, digital cameras, camcorders,viewfinders, micro-displays that are less than 2 inches diagonal, 3-Ddisplays, virtual reality or augmented reality displays, vehicles, videowalls comprising multiple displays tiled together, theater or stadiumscreens, or signs. Various control mechanisms may be used to controldevices fabricated in accordance with the present invention, includingpassive matrix and active matrix. Many of the devices are intended foruse in a temperature range comfortable to humans, such as 18 degrees C.to 30 degrees C., and more preferably at room temperature (20-25 degreesC.), but could be used outside this temperature range, for example, from−40 degree C. to +80 degree C.

The materials and structures described herein may have applications indevices other than OLEDs. For example, other optoelectronic devices suchas organic solar cells and organic photodetectors may employ thematerials and structures. More generally, organic devices, such asorganic transistors, may employ the materials and structures.

The term “halo,” “halogen,” or “halide” as used herein includesfluorine, chlorine, bromine, and iodine.

The term “alkyl” as used herein means a straight or branched chainsaturated acyclic hydrocarbon radical, which may optionally besubstituted with any suitable substituent. Accordingly, an alkyl radicalin accordance with the present invention can comprise any combination ofprimary, secondary, tertiary and quaternary carbon atoms. Exemplaryalkyl radicals include, but are not limited to, C₁-C₂₀-alkyl,C₁-C₁₈-alkyl, C₁-C₁₆-alkyl, C₁-C₁₄-alkyl, C₁-C₁₂-alkyl, C₁-C₁₀-alkyl,C₁-C₈-alkyl, C₁-C₆-alkyl, C₁-C₄-alkyl, C₁-C₃-alkyl, and C₂-alkyl.Specific examples include methyl, ethyl, 1-propyl, 2-propyl,2-methyl-1-propyl, 1-butyl, 2-butyl, t-butyl, n-octyl, n-decyl, andn-hexadecyl.

As used herein, the term “heteroalkyl” refers to an alkyl group asdescribed herein in which one or more carbon atoms is replaced by aheteroatom. Suitable heteroatoms include oxygen, sulfur, nitrogen,phosphorus, and the like. Examples of heteroalkyl groups include, butare not limited to, alkoxy, amino, thioester, poly(ethylene glycol), andalkyl-substituted amino.

The term “cycloalkyl” as used herein contemplates cyclic alkyl radicals.Preferred cycloalkyl groups are those containing 3 to 7 carbon atoms andincludes cyclopropyl, cyclopentyl, cyclohexyl, and the like.Additionally, the cycloalkyl group may be optionally substituted.

As used herein, the term “alkenyl” means acyclic branched or unbranchedhydrocarbon radical having one or more carbon-carbon double bonds.Exemplary alkenyl radicals include, but are not limited to,C₁-C₂₀-alkenyl radical, C₂-C₁₈-alkenyl radical, C₂-C₁₆-alkenyl radical,C₂-C₁₄-alkenyl radical, C₂-C₁₂-alkenyl radical, C₂-C₁₀-alkenyl radical,C₂-C₈-alkenyl radical, C₂-C₆-alkenyl radical, C₂-C₄-alkenyl radical,C₂-C₃-alkenyl radical, and C₂-alkenyl radical. Specific examplesinclude, but are not limited to, ethylenyl, propylenyl, 1-butenyl,2-butenyl, isobutylenyl, 1-pentenyl, 2-pentenyl, 3-methyl-1-butenyl,2-methyl-2-butenyl, and 2,3-dimethyl-2-butenyl.

As used herein, the term “alkylene” means an optionally substitutedsaturated straight or branched chain hydrocarbon radical. Exemplaryalkylene radicals include, but are not limited to, C₁-C₂₀-alkylene,C₂-C₁₈-alkylene, C₂-C₁₆-alkylene, C₂-C₁₄-alkylene, C₂-C₁₂-alkylene,C₂-C₁₀-alkylene, C₂-C₈-alkylene, C₂-C₆-alkylene, C₂-C₄-alkylene,C₂-C₃-alkylene, and C₂-alkylene. Specific examples of alkylene include,but are not limited to, methylene, dimethylene, and trimethylene.

As used herein, the term “alkynyl” means an acyclic branched orunbranched hydrocarbon having at least one carbon-carbon triple bond.Exemplary alkylene radicals include, but are not limited to,C₁-C₂₀-alkynyl radical, C₂-C₁₈-alkynyl radical, C₂-C₁₆-alkynyl radical,C₂-C₁₄-alkynyl radical, C₂-C₁₂-alkynyl radical, C₂-C₁₀-alkynyl radical,C₂-C₈-alkynyl radical, C₂-C₆-alkynyl radical, C₂-C₄-alkynyl radical,C₂-C₃-alkynyl radical, and C₂-alkynyl radical. Specific examples ofalkynyl include, but are not limited to, propargyl, and 3-pentynyl,acetylenyl, propynyl, 1-butynyl, 2-butynyl, 1-pentynyl, 2-pentynyl, and3-methyl-1-butynyl.

As used herein, the term “aralkyl” means one or more aryl radicals asdefined herein attached through an alkyl bridge (e.g., -alkylaryl)_(j),wherein j is 1, 2 or 3). Specific examples of aralkyl include, but arenot limited to, benzyl (—CH₂-phenyl, i.e., Bn), diphenyl methyl(—CH₂-(phenyl)₂) and trityl (—C-(phenyl)₃). Additionally, the aralkylgroup may be optionally substituted.

Unless stated otherwise, as used herein, the term “heterocycle” andvariants of the term, including “heterocyclic group” and “heterocyclyl,”means an optionally substituted monocyclic or polycyclic ring systemhaving as ring members atoms of at least two different elements andwherein the monocyclic or polycyclic ring system is either saturated,unsaturated or aromatic. In some embodiments, heterocyle comprisescarbon atoms and at least one heteroatom. In some embodiments,heterocyle comprises carbon atoms and at least one heteroatom selectedfrom nitrogen, oxygen, silicon, selenium, and sulfur, and wherein thenitrogen, oxygen, silicon, selenium, and sulfur heteroatoms may beoptionally oxidized, and the nitrogen heteroatom may be optionallyquaternized. Examples of heterocycle include, but are not limited to,furyl, benzofuranyl, thiophenyl, benzothiophenyl, pyrrolyl, indolyl,isoindolyl, azaindolyl, pyridyl, quinolinyl, isoquinolinyl, oxazolyl,isooxazolyl, benzoxazolyl, pyrazolyl, imidazolyl, benzimidazolyl,thiazolyl, benzothiazolyl, isothiazolyl, pyridazinyl, pyrimidinyl,pyrazinyl, triazinyl, cinnolinyl, phthalazinyl, and quinazolinyl. Thus,in addition to the aromatic heteroaryls listed above, heterocycles alsoinclude (but are not limited to) morpholinyl, pyrrolidinonyl,pyrrolidinyl, piperizinyl, piperidinyl, hydantoinyl, valerolactamyl,oxiranyl, oxetanyl, tetrahydrofuranyl, tetrahydropyranyl,tetrahydropyridinyl, tetrahydroprimidinyl, tetrahydrothiophenyl,tetrahydrothiopyranyl, tetrahydropyrimidinyl, tetrahydrothiophenyl, andtetrahydrothiopyranyl.

As used herein, the term “aryl” means an optionally substitued monoyclicor polycyclic aromatic hydrocarbon. Specific examples of aryl include,but are not limited to, phenyl, phenyl, 4-methylphenyl,2,6-dimethylphenyl, naphthyl, anthracenyl, and phenanthrenyl. The term“aryl” or “aromatic group” as used herein contemplates single-ringgroups and polycyclic ring systems. The polycyclic rings may have two ormore rings in which two carbons are common to two adjoining rings (therings are “fused”) wherein at least one of the rings is aromatic, e.g.,the other rings can be cycloalkyls, cycloalkenyls, aryl, heterocycles,and/or heteroaryls. Additionally, the aryl group may be optionallysubstituted.

As used herein, the term “heteroaryl” means an optionally substitutedmonoyclic or polycyclic aromatic hydrocarbon having at least oneheteroatom and at least one carbon atom. In some embodiments, the atleast one heteroatom is selected from nitrogen, oxygen, silicon,selenium, and sulfur. Specific examples of heteroaryl include, but arenot limited to, furyl, benzofuranyl, thiophenyl, benzothiophenyl,pyrrolyl, indolyl, isoindolyl, azaindolyl, pyridyl, quinolinyl,isoquinolinyl, oxazolyl, isooxazolyl, benzoxazolyl, pyrazolyl,imidazolyl, benzimidazolyl, thiazolyl, benzothiazolyl, isothiazolyl,pyridazinyl, pyrimidinyl, pyrazinyl, triazinyl, cinnolinyl,phthalazinyl, and quinazolinyl.

The alkyl, cycloalkyl, alkenyl, alkynyl, aralkyl, heterocyclic group,aryl, and heteroaryl may be optionally substituted with one or moresubstituents selected from the group consisting of hydrogen, deuterium,halogen, alkyl, cycloalkyl, heteroalkyl, arylalkyl, alkoxy, aryloxy,amino, cyclic amino, silyl, alkenyl, cycloalkenyl, heteroalkenyl,alkynyl, aryl, heteroaryl, acyl, carbonyl, carboxylic acid, ether,ester, nitrile, isonitrile, sulfanyl, sulfinyl, sulfonyl, phosphino, andcombinations thereof.

As used herein, “substituted” indicates that a substituent other than His bonded to the relevant position, such as carbon. Thus, for example,where R¹ is mono-substituted, then one R¹ must be other than H.Similarly, where R¹ is di-substituted, then two of R¹ must be other thanH. Similarly, where R¹ is unsubstituted, R¹ is hydrogen for allavailable positions.

The “aza” designation in the fragments described herein, i.e.aza-dibenzofuran, aza-dibenzothiophene, etc. means that one or more ofthe C—H groups in the respective fragment can be replaced by a nitrogenatom, for example, and without any limitation, azatriphenyleneencompasses both dibenzo[f,h]quinoxaline and dibenzo[f,h]quinoline. Oneof ordinary skill in the art can readily envision other nitrogen analogsof the aza-derivatives described above, and all such analogs areintended to be encompassed by the terms as set forth herein.

It is to be understood that when a molecular fragment is described asbeing a substituent or otherwise attached to another moiety, its namemay be written as if it were a fragment (e.g. phenyl, phenylene,naphthyl, dibenzofuryl) or as if it were the whole molecule (e.g.benzene, naphthalene, dibenzofuran). As used herein, these differentways of designating a substituent or attached fragment are considered tobe equivalent.

As used herein, and as would be generally understood by one skilled inthe art, a first “Highest Occupied Molecular Orbital” (HOMO) or “LowestUnoccupied Molecular Orbital” (LUMO) energy level is “greater than” or“higher than” a second HOMO or LUMO energy level if the first energylevel is closer to the vacuum energy level. Since ionization potentials(IP) are measured as a negative energy relative to a vacuum level, ahigher HOMO energy level corresponds to an IP having a smaller absolutevalue (an IP that is less negative). Similarly, a higher LUMO energylevel corresponds to an electron affinity (EA) having a smaller absolutevalue (an EA that is less negative). On a conventional energy leveldiagram, with the vacuum level at the top, the LUMO energy level of amaterial is higher than the HOMO energy level of the same material. A“higher” HOMO or LUMO energy level appears closer to the top of such adiagram than a “lower” HOMO or LUMO energy level.

As used herein, the term “triplet energy” refers to an energycorresponding to the highest energy feature discernable in thephosphorescence spectrum of a given material. The highest energy featureis not necessarily the peak having the greatest intensity in thephosphorescence spectrum, and could, for example, be a local maximum ofa clear shoulder on the high energy side of such a peak.

According to an aspect of the present disclosure, a compound having astructure (L_(A))_(n)ML_(m) according to Formula 1,

is disclosed. In Formula 1, M is a metal having an atomic weight greaterthan 40, n has a value of at least 1 and m+n is the maximum number ofligands that may be attached to the metal;wherein A is a linking group selected from the group consisting of A1thorough A222 shown below; wherein any one of the ring atoms to whichR^(1b) to R^(1g) are attached may be replaced with a nitrogen atom,wherein when the ring atom is replaced with a nitrogen atom thecorresponding R group is not present; andwherein L is a substituted or unsubstituted cyclometallated ligand;wherein R^(1a) is selected from the group consisting of:

wherein R^(1b) is selected from the group consisting of:

wherein R^(1c) is selected from the group consisting of:

wherein R^(1d) is selected from the group consisting of:

wherein R^(1e) is selected from the group consisting of:

wherein R^(1f) is selected from the group consisting of:

wherein which R^(1g)=H;wherein the structures A1 through A222 are:

In some embodiments of the compound, the ligand L_(A) is one of theligands defined by L_(Ai) designated using the formulaA^(Z)-R^(1aj)—R^(1bk)—R^(1cl)—R^(1dm)—R^(1en)—R^(1fo)—R^(1g); wherein Zis an integer from 1 to 222 whereby A^(Z) represents A1 through A222;wherein j is an integer from 1 to 6; and k, l, m, n and o are integersfrom 1 to 5; whereini=222((6((5((5((5((5(o−1)+n)−1)+m)−1)+l)−1)+k)−1)+j)−1)+Z.

In some embodiments of the compound, the compound has a triplet excitedstate and wherein the linking group A stabilizes the bond between N² andC^(1b) from cleavage when the compound is in the triplet excited state.

In one embodiment, the compound has a triplet excited state and whereinthe linking group A stabilizes the bond between N² and C^(1b) fromcleavage when the compound is in the triplet excited state.

In one embodiment, the compound has a peak emissive wavelength less than500 nm. In another embodiment, the compound has a peak emissivewavelength less than 480 nm. In yet another embodiment, the compound hasa peak emissive wavelength ranging from 400 nm to 500 nm.

In some embodiments, the compound is selected from the group consistingof:

In some embodiments of the compound having Formula 1, the metal isselected from the group consisting of Re, Ru, Os, Rh, Ir, Pd, Pt, andAu. In some embodiments, the metal is selected from the group consistingof Ir and Pt.

In some embodiments of the compound of Formula 1, the ligand L isselected from the group consisting of:

wherein each X¹ to X¹³ are independently selected from the groupconsisting of carbon and nitrogen;

wherein X is selected from the group consisting of BR′, NR′, PR′, O, S,Se, C═O, S═O, SO₂, CR′R″, SiR′R″, and GeR′R″;

wherein R′ and R″ are optionally fused or joined to form a ring;

wherein each R_(a), R_(b), R_(c), and R_(d) may represent from monosubstitution to the possible maximum number of substitution, or nosubstitution;

wherein R′, R″, R_(a), R_(b), R_(c), and R_(d) are each independentlyselected from the group consisting of hydrogen, deuterium, halide,alkyl, cycloalkyl, heteroalkyl, arylalkyl, alkoxy, aryloxy, amino,silyl, alkenyl, cycloalkenyl, heteroalkenyl, alkynyl, aryl, heteroaryl,acyl, carbonyl, carboxylic acids, ester, nitrile, isonitrile, sulfanyl,sulfinyl, sulfonyl, phosphino, and combinations thereof; and

wherein any two adjacent substitutents of R_(a), R_(b), R_(c), and R_(d)are optionally fused or joined to form a ring or form a multidentateligand.

In some embodiments of the compound of Formula 1, the ligand L isselected from the group consisting of:

wherein R_(a) and R_(b) are as defined above.

In some embodiments of the compound of Formula 1, the ligand L isselected from the group consisting of:

wherein R_(a) and R_(b) are as defined above.

In some embodiments of the compound of Formula 1, the ligand L isselected from the group consisting of:

wherein R_(a), R_(b), and R_(c) are as defined above.

In some embodiments of the compound of Formula 1, ligand L is selectedfrom the group consisting of:

In some embodiments of the compound of Formula 1, the compound is(L_(A))₃Ir, wherein L_(A) is as defined above.

In some embodiments of the compound of Formula 1, the compound is(L_(A))Ir(L)₂ or (L_(A))₂Ir(L), wherein L_(A) and L are as definedabove.

The compound of claim 2, wherein the compound is Compound A-x havingformula of (L_(Ai))₃Ir, Compound B-y having formula of(L_(Ai))Ir(L_(q))₂, or Compound C-z having formula of(L_(Ai))₂Ir(L_(q));

wherein i is defined in claim 2, q is an integer from 1 to 254;wherein x=i, y=254(i−1)+q, z=254(i−1)+q.wherein L₁ to L₂₅₄ have the following structures:

In some embodiments of the compound, the compound has a structure ofFormula 2:

wherein M is Pt;

wherein A¹ and A² are linking groups, each independently selected fromthe group consisting of A1 through A222;

wherein R^(2b), R^(2c), R^(2d), R^(2e), and R^(2f) are independentlyselected from the same respective groups as for R^(1b), R^(1c), R^(1d),R^(1e), and R^(1f),

wherein any one of the ring atoms to which R^(1b) to R^(1f) and R^(2b)to R^(2f) are attached may be replaced with a nitrogen atom, whereinwhen the ring atom is replaced with a nitrogen atom the corresponding Rgroup is not present; and

wherein R^(ab) and R^(ac) and/or R^(ga) and R^(gb) may bond to form asecond linking group having one to three linking atoms eachindependently selected from the group consisting of B, N, P, O, S, Se,C, Si, Ge or combinations thereof

In some embodiments of the compound of Formula 2, the compound has atriplet excited state and wherein the linking group A stabilizes thebond between N² and C^(1b) from cleavage when the compound is in thetriplet excited state.

In some embodiments of the compound of Formula 2, the compound has apeak emissive wavelength less than 500 nm. In some embodiments, thecompound has a peak emissive wavelength less than 480 nm. In someembodiments, the compound has a peak emissive wavelength ranging from400 nm to 500 nm.

According to another aspect of the present disclosure, an organic lightemitting device (OLED) is disclosed. The OLED comprises: an anode; acathode; and an organic layer, disposed between the anode and thecathode, comprising a compound having a structure (L_(A))_(n)ML_(m)according to Formula 1:

wherein M is a metal having an atomic weight greater than 40, n has avalue of at least 1 and m+n is the maximum number of ligands that may beattached to the metal;

wherein A is a linking group selected from the group consisting of A1thorough A222 shown below;

wherein any one of the ring atoms to which R^(1b) to R^(1g) are attachedmay be replaced with a nitrogen atom, wherein when the ring atom isreplaced with a nitrogen atom the corresponding R group is not present;and

wherein L is a substituted or unsubstituted cyclometallated ligand;

wherein R^(1a) is selected from the group consisting of:

wherein R^(1b) is selected from the group consisting of:

wherein R^(1c) is selected from the group consisting of:

wherein R^(1d) is selected from the group consisting of:

wherein R^(1e) is selected from the group consisting of:

wherein R^(1f) is selected from the group consisting of:

wherein which R^(1g)=H;

wherein the structures A1 through A222 are:

According to another aspect, a consumer product comprising an OLED isdisclosed, wherein the OLED comprises: an anode; a cathode; and anorganic layer, disposed between the anode and the cathode. The organiclayer comprising a compound having a structure (L_(A))_(n)ML_(m)according to Formula 1:

defined herein.

In some embodiments of the OLED, the organic layer is an emissive layerand the compound is an emissive dopant or a non-emissive dopant.

In some embodiments of the OLED, the organic layer further comprises ahost, wherein the host comprises a triphenylene containing benzo-fusedthiophene or benzo-fused furan;

wherein any substituent in the host is an unfused substituentindependently selected from the group consisting of C_(n)H_(2n+1),OC_(n)H_(2n+1), OAr₁, N(C_(n)H_(2n+1))₂, N(Ar₁)(Ar₂),CH═CH—C_(n)H_(2n+1), C≡CC_(n)H_(2n+1), Ar₁, Ar₁—Ar₂, andC_(n)H_(2n)—Ar₁, or the host has no substitution;

wherein n is from 1 to 10; and

wherein Ar₁ and Ar₂ are independently selected from the group consistingof benzene, biphenyl, naphthalene, triphenylene, carbazole, andheteroaromatic analogs thereof.

In some embodiments of the OLED, the organic layer further comprises ahost, wherein host comprises at least one chemical group selected fromthe group consisting of triphenylene, carbazole, dibenzothiphene,dibenzofuran, dibenzoselenophene, azatriphenylene, azacarbazole,aza-dibenzothiophene, aza-dibenzofuran, and aza-dibenzoselenophene.

According to another aspect of the present disclosure, a formulationcomprising a compound of Formula 1 is also disclosed. The formulationcan include one or more components selected from the group consisting ofa solvent, a host, a hole injection material, hole transport material,and an electron transport layer material, disclosed herein.

Organic light-emitting materials according to various embodiments of theinvention can exhibit a number of desirable characteristics. In someembodiments, the organic light-emitting materials can exhibitphotoluminescence with a high quantum efficiency, with a narrow spectralwidth, and with a peak emission wavelength located within a desirablerange of wavelengths, such as the visible range or the near infraredrange. Also, these photoluminescent characteristics can be relativelyinvariant over a wide range of excitation wavelengths. The organiclight-emitting materials can have other desirable characteristics, suchas relating to their band gap energies and electrical conductivities.Advantageously, the organic light-emitting materials can beinexpensively and readily formed for use in various applications,including consumer products and lighting panels.

In some embodiments, the content of a photoluminescent substance in alight emitting material according to the present invention is between0.1% by mass to 50% by mass inclusive with respect to the total mass ofa light emitting layer comprising the light emitting material. In someembodiments, the content of a photoluminescent substance in a lightemitting material according to the present invention is between 0.3% bymass to 40% by mass inclusive with respect to the total mass of a lightemitting layer comprising the light emitting material. In someembodiments, the content of a photoluminescent substance in a lightemitting material according to the present invention is between 0.5% bymass to 30% by mass inclusive with respect to the total mass of a lightemitting layer comprising the light emitting material. In someembodiments, the photoluminescent substance in a light emitting materialaccording to the present invention is appended to a polymer chain orincorporated in a denrimer material.

IV. Devices

In some aspects, the present invention provides an organicelectroluminescence device which comprises at least one metal complexhaving the structure of Formula 1, Formula 2, or Formula 3. In someembodiments, an organic electroluminescence device according to thepresent invention comprises a first organic light emitting device, whichfurther comprises an anode; a cathode; an organic layer disposed betweenthe anode and the cathode, and comprising at least one metal complexhaving the structure of Formula 1, Formula 2, or Formula 3. In somepreferred embodiments of the organic electroluminescence device, theorganic layer further comprises a host material. In some preferredembodiments of the organic electroluminescence device, the host materialcomprises an organic compound. In some preferred embodiments of theorganic electroluminescence device, the host material comprises anorganic compound having a molecule containing at least one groupselected from the group consisting of carbazole, dibenzothiphene,dibenzofuran, azacarbazole, aza-dibenzothiophene, and aza-dibenzofuran.

Generally, an organic layer suitable for use in the organicelectroluminescence device of the present may have any suitableconfiguration of layer depending, for example, on application andpurpose of the organic electroluminescence device. Accordingly, in someembodiments of the organic electroluminescence device, the organic layeris formed on a transparent electrode or a semitransparent electrode. Insome such embodiments, the organic layer is formed on a top surface orany suitable surface of the transparent electrode or the semitransparentelectrode. Also, suitable shape, size and/or thickness of the organiclayer may be employed depending, for example, on application and thepurpose of the organic electroluminescence device. Specific examples ofconfigurations of an organic electroluminescence device of the presentinvention, having a substrate, a cathode, an anode and an organic layerinclude, but are not limited to, the following:

-   -   (A) Anode/hole transporting layer/light emitting layer/electron        transporting layer/cathode;    -   (B) Anode/hole transporting layer/light emitting layer/block        layer/electron transporting layer/cathode;    -   (C) Anode/hole transporting layer/light emitting layer/block        layer/electron transporting layer/electron injection        layer/cathode;    -   (D) Anode/hole injection layer/hole transporting layer/light        emitting layer/block layer/electron transporting layer/cathode;        and    -   (E) Anode/hole injection layer/hole transporting layer/light        emitting layer/block layer/electron transporting layer/electron        injection layer/cathode.    -   (F) Anode/hole injection layer/electron blocking layer/hole        transporting layer/light emitting layer/block layer/electron        transporting layer/electron injection layer/cathode.

Additional device configuration, including substrate, cathode and anodeof an organic electroluminescence device, is described in JapanesePatent Publication No. 2008-270736.

<Substrate>

A suitable substrate usable in an organic electroluminescence device ofthe present invention is preferably a substrate which does not scatteror decrease light emitted from an organic layer when used for displayapplications. When used for lighting or certain display applications,substrates that scatter light are acceptable. In some embodiments, thesubstrate preferably is composed of an organic material which exhibitssuperior heat resistance, dimensional stability, solvent resistance,electrical insulating property and/or processability.

The substrate suitable for use in the present invention is preferablyone which does not scatter or attenuate light emitted from the organiccompound layer. Specific examples of materials for the substrate,include but are not limited to, inorganic materials such aszirconia-stabilized yttrium (YSZ) and glass; polyesters such aspolyethylene terephthalate, polybutylene phthalate, and polyethylenenaphthalate; and organic materials such as polystyrene, polycarbonate,polyethersulfone, polyarylate, polyimide, polycycloolefin, norborneneresin, polychlorotrifluoroethylene, and the like.

In some embodiments, when glass is used as the substrate, alkali freeglass is preferably used. Specific examples of suitable alkali freeglass are found in US patent application publication no. 2013/0237401 byTakahiro Kawaguchi, which published Sep. 12, 2013. In some embodiments,when soda-lime glass is used as the substrate, it is preferred to useglass on which a barrier coat of silica or the like has been applied. Insome embodiments, when an organic material is used as the substrate, itis preferred to use a material having one or more of the attributes:excellent in heat resistance, dimensional stability, solvent resistance,electric insulation performance, and workability.

Generally, there is no particular limitation as to the shape, thestructure, the size or the like of the substrate, but any of theseattributes may be suitably selected according to the application,purposes and the like of the light-emitting element. n general, aplate-like substrate is preferred as the shape of the substrate. Astructure of the substrate may be a monolayer structure or a laminatestructure. Furthermore, the substrate may be formed from a single memberor two or more members.

Although the substrate may be transparent and colorless, or transparentand colored, it is preferred that the substrate is transparent andcolorless from the viewpoint that the substrate does not scatter orattenuate light emitted from the organic light-emitting layer. In someembodiments, a moisture permeation preventive layer (gas barrier layer)may be provided on the top surface or the bottom surface of thesubstrate. Examples of a material of the moisture permeation preventivelayer (gas barrier layer), include, but are not limited to, inorganicsubstances such as silicon nitride and silicon oxide. The moisturepermeation preventive layer (gas barrier layer) may be formed inaccordance with, for example, a high-frequency sputtering method or thelike.

In the case of applying a thermoplastic substrate, a hard-coat layer oran under-coat layer may be further provided as needed.

<Anode>

Any anode may be used in an organic electroluminescence device of thepresent invention so long as it serves as an electrode supplying holesinto an organic layer. In some embodiments of the organicelectroluminescence device of the present invention, any suitable shape,structure and/or size of known electrode material may be used depending,for example, on the application and purpose of the organicelectroluminescence device. In some embodiments, a transparent anode ispreferred.

The anode may generally be any material as long as it has a function asan electrode for supplying holes to the organic compound layer, andthere is no particular limitation as to the shape, the structure, thesize or the like. However, it may be suitably selected from amongwell-known electrode materials according to the application and purposeof the light-emitting element. In some embodiments, the anode isprovided as a transparent anode.

Materials for the anode preferably include, for example, metals, alloys,metal oxides, electric conductive compounds, and mixtures thereof.Materials having a work function of 4.0 eV or more are preferable.Specific examples of the anode materials include electric conductivemetal oxides such as tin oxides doped with antimony, fluorine or thelike (ATO and FTO), tin oxide, zinc oxide, indium oxide, indium tinoxide (ITO), and indium zinc oxide (IZO); metals such as gold, silver,chromium, aluminum, copper, and nickel; mixtures or laminates of thesemetals and the electric conductive metal oxides; inorganic electricconductive materials such as copper iodide and copper sulfide; organicelectric conductive materials such as polyaniline, polythiophene, andpolypyrrole; and laminates of these inorganic or organicelectron-conductive materials with ITO. Among these, the electricconductive metal oxides are preferred, and particularly, ITO ispreferable in view of productivity, high electric conductivity,transparency and the like.

The anode may be formed on the substrate in accordance with a methodwhich is appropriately selected from among wet methods such as printingmethods, coating methods and the like; physical methods such as vacuumdeposition methods, sputtering methods, ion plating methods and thelike; and chemical methods such as CVD (chemical vapor deposition) andplasma CVD methods and the like, in consideration of the suitability toa material constituting the anode. For instance, when ITO is selected asa material for the anode, the anode may be formed in accordance with aDC or high-frequency sputtering method, a vacuum deposition method, anion plating method or the like.

In the organic electroluminescence element of the present invention, aposition at which the anode is to be formed is not particularly limited,but it may be suitably selected according to the application and purposeof the light-emitting element. The anode may be formed on either thewhole surface or a part of the surface on either side of the substrate.

For patterning to form the anode, a chemical etching method such asphotolithography, a physical etching method such as etching by laser, amethod of vacuum deposition or sputtering through superposing masks, ora lift-off method or a printing method may be applied.

A thickness of the anode may be suitably selected according to thematerial constituting the anode and is therefore not definitely decided,but it is usually in a range of from 10 nm to 50 μm, and preferably from50 nm to 20 μm. The thickness of the anode layer may be properlycontrolled depending on the material used therefor. The resistance ofthe anode is preferably 10³ Ω/square or less, and more preferably 10²Ω/square or less, more preferably 30 Ω/square or less. In the case wherethe anode is transparent, it may be either transparent and colorless, ortransparent and colored. For extracting luminescence from thetransparent anode side, it is preferred that a light transmittance ofthe anode is 60% or higher, and more preferably 70% or higher. Adetailed description of transparent anodes can be found in “TOUMEIDENNKYOKU-MAKU NO SHINTENKAI (Novel Developments in TransparentElectrode Films)” edited by Yutaka Sawada, published by C.M.C. in 1999.

In the case where a plastic substrate having a low heat resistance isused in the present invention, it is preferred that ITO or IZO is usedto obtain a transparent anode prepared by forming the film at a lowtemperature of 150° C. or lower.

<Cathode>

Any cathode may be used in an organic electroluminescence device of thepresent invention so long as it serves as an electrode supplyingelectrons into the organic layer. In some embodiments of the organicelectroluminescence device of the present invention, any suitable shape,structure and/or size of known electrode material may be used depending,for example, on the application and purpose of the organicelectroluminescence device. In some embodiments, a transparent cathodeis preferred.

The cathode may generally be any material as long as it has a functionas an electrode for injecting electrons to the organic compound layer,and there is no particular limitation as to the shape, the structure,the size or the like. However it may be suitably selected from amongwell-known electrode materials according to the application and purposeof the light-emitting element.

Materials constituting the cathode include, for example, metals, alloys,metal oxides, electric conductive compounds, and mixtures thereof.Materials having a work function of 4.0 eV or more are preferable.Specific examples thereof include alkali metals (e.g., Li, Na, K, Cs orthe like), alkaline earth metals (e.g., Mg, Ca or the like), gold,silver, lead, aluminum, sodium-potassium alloys, lithium-aluminumalloys, magnesium-silver alloys, rare earth metals such as indium, andytterbium, and the like. They may be used alone, but it is preferredthat two or more of them are used in combination from the viewpoint ofsatisfying both stability and electron injectability.

In some embodiments, as the materials for constituting the cathode,alkaline metals or alkaline earth metals are preferred in view ofelectron injectability, and materials containing aluminum as a majorcomponent are preferred in view of excellent preservation stability.

The term “material containing aluminum as a major component” refers to amaterial constituted by aluminum alone; alloys comprising aluminum and0.01% by weight to 10% by weight of an alkaline metal or an alkalineearth metal; or mixtures thereof (e.g., lithium-aluminum alloys,magnesium-aluminum alloys and the like). Exemplary materials for thecathode are described in detail in JP-A Nos. 2-15595 and 5-121172.

A method for forming the cathode is not particularly limited, but it maybe formed in accordance with a well-known method. For instance, thecathode may be formed in accordance with a method which is appropriatelyselected from among wet methods such as printing methods, coatingmethods and the like; physical methods such as vacuum depositionmethods, sputtering methods, ion plating methods and the like; andchemical methods such as CVD and plasma CVD methods and the like, inconsideration of the suitability to a material constituting the cathode.For example, when a metal (or metals) is (are) selected as a material(or materials) for the cathode, one or two or more of them may beapplied at the same time or sequentially in accordance with a sputteringmethod or the like.

For patterning to form the cathode, a chemical etching method such asphotolithography, a physical etching method such as etching by laser, amethod of vacuum deposition or sputtering through superposing masks, ora lift-off method or a printing method may be applied.

In the present invention, a position at which the cathode is to beformed is not particularly limited, and it may be formed on either thewhole or a part of the organic compound layer.

Furthermore, a dielectric material layer made of fluorides, oxides orthe like of an alkaline metal or an alkaline earth metal may be insertedbetween the cathode and the organic compound layer with a thickness offrom 0.1 nm to 5 nm. The dielectric material layer may be considered tobe a kind of electron injection layer. The dielectric material layer maybe formed in accordance with, for example, a vacuum deposition method, asputtering method, an ionplating method or the like.

A thickness of the cathode may be suitably selected according tomaterials for constituting the cathode and is therefore not definitelydecided, but it is usually in a range of from 10 nm to 5 μm, andpreferably from 50 nm to 1 μm.

Moreover, the cathode may be transparent or opaque. A transparentcathode may be formed by preparing a material for the cathode with asmall thickness of from 1 nm to 10 nm, and further laminating atransparent electric conductive material such as ITO or IZO thereon.

<Protective Layer>

A whole body of the organic EL element of the present invention may beprotected by a protective layer. Any materials may be applied in theprotective layer as long as the materials have a function to protect apenetration of ingredients such as moisture, oxygen or the like whichaccelerates deterioration of the element into the element. Specificexamples of materials for the protective layer include metals such asIn, Sn, Pb, Au, Cu, Ag, Al, Ti, Ni and the like; metal oxides such asMgO, SiO, SiO₂, Al₂O₃, GeO, NiO, CaO, BaO, Fe₂O₃, Y₂O₃, TiO₂ and thelike; metal nitrides such as SiN_(x), SiN_(x)O_(y) and the like; metalfluorides such as MgF₂, LiF, AlF₃, CaF₂ and the like; polyethylene;polypropylene; polymethyl methacrylate; polyimide; polyurea;polytetrafluoroethylene; polychlorotrifluoroethylene;polydichlorodifluoroethylene; a copolymer of chlorotrifluoroethylene anddichlorodifluoroethylene; copolymers obtained by copolymerizing amonomer mixture containing tetrafluoroethylene and at least onecomonomer; fluorine-containing copolymers each having a cyclic structurein the copolymerization main chain; water-absorbing materials eachhaving a coefficient of water absorption of 1% or more; moisturepermeation preventive substances each having a coefficient of waterabsorption of 0.1% or less; and the like.

There is no particular limitation as to a method for forming theprotective layer. For instance, a vacuum deposition method, a sputteringmethod, a reactive sputtering method, an MBE (molecular beam epitaxial)method, a cluster ion beam method, an ion plating method, a plasmapolymerization method (high-frequency excitation ion plating method), aplasma CVD method, a laser CVD method, a thermal CVD method, a gassource CVD method, a coating method, a printing method, or a transfermethod may be applied.

<Sealing>

The whole organic electroluminescence element of the present inventionmay be sealed with a sealing cap. Furthermore, a moisture absorbent oran inert liquid may be used to seal a space defined between the sealingcap and the light-emitting element. Although the moisture absorbent isnot particularly limited, specific examples thereof include bariumoxide, sodium oxide, potassium oxide, calcium oxide, sodium sulfate,calcium sulfate, magnesium sulfate, phosphorus pentaoxide, calciumchloride, magnesium chloride, copper chloride, cesium fluoride, niobiumfluoride, calcium bromide, vanadium bromide, molecular sieve, zeolite,magnesium oxide and the like. Although the inert liquid is notparticularly limited, specific examples thereof include paraffins;liquid paraffins; fluorine-based solvents such as perfluoroalkanes,perfluoroamines, perfluoroethers and the like; chlorine-based solvents;silicone oils; and the like.

<Driving>

In the organic electroluminescence element of the present invention,when a DC (AC components may be contained as needed) voltage (usually 2volts to 15 volts) or DC is applied across the anode and the cathode,luminescence can be obtained. For the driving method of the organicelectroluminescence element of the present invention, driving methodsdescribed in JP-A Nos. 2-148687, 6-301355, 5-29080, 7-134558, 8-234685,and 8-241047; Japanese Patent No. 2784615, U.S. Pat. Nos. 5,828,429 and6,023,308 are applicable.

<Applications>

Devices fabricated in accordance with embodiments of the inventionsdescribed herein may be incorporated into a wide variety of consumerproducts, including but not limited to flat panel displays, computermonitors, televisions, billboards, lights for interior or exteriorillumination and/or signaling, heads up displays, fully transparentdisplays, flexible displays, laser printers, telephones, cell phones,personal digital assistants (PDAs), laptop computers, digital cameras,camcorders, viewfinders, micro-displays, vehicles, a large area wall,theater or stadium screen, or a sign.

<Organic Layer>

An organic layer suitable for use in an organic electroluminescencedevice of the present invention may comprise a plurality of layers,including, for example, light emitting layer, host material, electriccharge transporting layer, hole injection layer, and hole transportinglayer. Blocking layers may also be included e.g. hole (and or exciton)blocking layers (HBL) or electron (and or exciton) blocking layers(EBL). In some embodiments of an organic electroluminescence device ofthe present invention, each organic layer may be formed by a dry-typefilm formation method such as a deposition method or a sputteringmethod, or a solution coating process such as a transfer method, aprinting method, a spin coating method, or a bar coating method. In someembodiments of an organic electroluminescence device of the presentinvention, at least one layer of the organic layer is preferably formedby a solution coating process.

A. Light Emitting Layer

Light Emitting Material:

A light emitting material in accordance with the present inventionpreferably includes at least one metal complex having the structure ofFormula 1, Formula 2, or Formula 3. Some embodiments of an organicelectroluminescence device of the present invention comprises the lightemitting material in an amount of about 0.1% by mass to about 50% bymass with respect to the total mass of the compound constituting thelight emitting layer. In some embodiments, an organicelectroluminescence device of the present invention comprises the lightemitting material in an amount of about 1% by mass to about 50% by masswith respect to the total mass of the compound constituting the lightemitting layer. In some embodiments, an organic electroluminescencedevice of the present invention comprises the light emitting material inan amount of about 2% by mass to about 40% by mass with respect to thetotal mass of the compound constituting the light emitting layer. Insome embodiments, a total amount of the light-emitting materials in thelight-emitting layer is preferably from about 0.1% by weight to about30% by weight with respect to the entire amount of compounds containedin the light-emitting layer. In some embodiments, a total amount of thelight-emitting materials in the light-emitting layer is preferably fromabout 1% by weight to about 20% by weight in view of durability andexternal quantum efficiency. In some embodiments, a total amount of thehost materials in the light-emitting layer is preferably from about 70%by weight to about 99.9% by weight. In some embodiments, a total amountof the host materials in the light-emitting layer is preferably fromabout 80% by weight to 99% by weight in view of durability and externalquantum efficiency. In some embodiments, graded light emitting layers orgraded interfaces within the light emitting layer may be used. Gradingmay be formed, for example, by mixing two or more distinct materials ina fashion that an abrupt change from one layer to another is not formed.Graded light emitting layers and or interfaces have been shown toimprove device lifetime and this device architecture may be beneficialto improving PHOLED lifetime and general performance. In this instancethe light emitting material may be present in an amount of about 0% bymass to about 100% by mass at any given position within the lightemitting layer.

In some embodiments, a light-emitting layer in the present invention mayinclude the light-emitting materials and a host material contained inthe light-emitting layer as a combination of a fluorescentlight-emitting material which emits light (fluorescence) through asinglet exciton and a host material, or a combination of aphosphorescent light-emitting material which emits light(phosphorescence) through a triplet exciton and a host material. In someembodiments, a light-emitting layer in the present invention may includethe light-emitting materials and a host material contained in thelight-emitting layer as a combination of a phosphorescent light-emittingmaterial and a host material.

In some embodiments, the first compound can be an emissive dopant. Insome embodiments, the compound can produce emissions viaphosphorescence, fluorescence, thermally activated delayed fluorescence,i.e., TADF (also referred to as E-type delayed fluorescence),triplet-triplet annihilation, or combinations of these processes.

B. Host Material

A suitable host material for use in the present invention, may be a holetransporting host material (sometimes referred to as a hole transportinghost), and/or an electron transporting host material (sometimes referredto as an electron transporting host).

The organic layer can also include a host. In some embodiments, two ormore hosts are preferred. In some embodiments, the hosts used maybe a)bipolar, b) electron transporting, c) hole transporting or d) wide bandgap materials that play little role in charge transport. In someembodiments, the host can include a metal complex. The host can be atriphenylene containing benzo-fused thiophene or benzo-fused furan. Anysubstituent in the host can be an unfused substituent independentlyselected from the group consisting of C_(n)H_(2n+1), OC_(n)H_(2n+1),OAr₁, N(C_(n)H_(2n+1))₂, N(Ar₁)(Ar₂), CH═CH—C_(n)H_(2n+1),C≡C—C_(n)H_(2n+1), Ar₁, Ar₁—Ar₂, and C_(n)H_(2n)—Ar₁, or the host has nosubstitution. In the preceding substituents n can range from 1 to 10;and Ar₁ and Ar₂ can be independently selected from the group consistingof benzene, biphenyl, naphthalene, triphenylene, carbazole, andheteroaromatic analogs thereof. In some embodiment, the host can also bean inorganic compound. For example a Zn containing inorganic material,e.g. ZnS.

The host can be a compound comprising at least one chemical groupselected from the group consisting of triphenylene, carbazole,dibenzothiophene, dibenzofuran, dibenzoselenophene, azatriphenylene,azacarbazole, aza-dibenzothiophene, aza-dibenzofuran, andaza-dibenzoselenophene. The host can include a metal complex. The hostcan be a specific compound selected from the group consisting of:

and combinations thereof.

Hole Transporting Host Material

Specific examples of the hole transporting host materials include, butare not limited to pyrrole, carbazole, azacarbazole, pyrazole, indole,azaindole, imidazole, polyarylalkane, pyrazoline, pyrazolone,phenylenediamine, arylamine, amino-substituted chalcone,styrylanthracene, fluorenone, hydrazone, stilbene, silazane, aromatictertiary amine compounds, styrylamine compounds, aromatic dimethylidinecompounds, porphyrin compounds, polysilane compounds,poly(N-vinylcarbazole), aniline copolymers, electric conductivehigh-molecular oligomers such as thiophene oligomers, polythiophenes andthe like, organic silanes, carbon films, derivatives thereof, and thelike. Some preferred host materials include carbazole derivatives,indole derivatives, imidazole derivatives, aromatic tertiary aminecompounds, and thiophene derivatives.

Electron Transporting Host Material

Specific examples of the electron transporting host materials include,but are not limited to pyridine, pyrimidine, triazine, imidazole,pyrazole, triazole, oxazole, oxadiazole, fluorenone,anthraquinonedimethane, anthrone, diphenylquinone, thiopyrandioxide,carbodiimide, fluorenylidenemethane, distyrylpyrazine,fluorine-substituted aromatic compounds, aromacyclic tetracarboxylicanhydrides of naphthalene, perylene or the like, phthalocyanine,derivatives thereof, including a variety of metal complexes representedby metal complexes of 8-quinolinol derivatives, metal phthalocyanine,and metal complexes having benzoxazole or benzothiazole as the ligand.

Preferable electron transporting hosts are metal complexes, azolederivatives (benzimidazole derivatives, imidazopyridine derivatives andthe like), and azine derivatives (pyridine derivatives, pyrimidinederivatives, triazine derivatives and the like).

C. Film Thickness

In some embodiments, the film thickness of the light-emitting layer ispreferably from about 10 nm to about 500 nm. In some embodiments, thefilm thickness of the light-emitting layer is preferably from about 20nm to about 100 nm depending, for example, on desired brightnessuniformity, driving voltage and brightness. In some embodiments, thelight-emitting layer is configured to have a thickness that optimizespassage of charges from the light-emitting layer to adjacent layerswithout lowering light-emission efficiency. In some embodiments, thelight-emitting layer is configured to have a thickness that maintainsminimum driving voltage maximum light-emission efficiency.

D. Layer Configuration

The light-emitting layer may be composed of a single layer or two ormore layers, and the respective layers may cause light emission indifferent light-emitting colors. Also, in the case where thelight-emitting layer has a laminate structure, though the film thicknessof each of the layers configuring the laminate structure is notparticularly limited, it is preferable that a total film thickness ofeach of the light-emitting layers falls within the foregoing range. Insome embodiments, graded layers or graded interfaces within the layersmay be used.

E. Hole Injection Layer and Hole Transport Layer

The hole injection layer and hole transport layer are layers functioningto receive holes from an anode or from an anode side and to transportthe holes to the emitting layer. Materials to be introduced into a holeinjection layer or a hole transport layer is not particularly limited,but either of a low molecular compound or a high molecular compound maybe used.

Specific examples of the material contained in the hole injection layerand the hole transport layer include, but are not limited to, pyrrolederivatives, carbazole derivatives, azacarbazole derivatives, indolederivatives, azaindole derivatives, imidazole derivatives,polyarylalkane derivatives, pyrazoline derivatives, pyrazolonederivatives, phenylenediamine derivatives, arylamine derivatives,amino-substituted chalcone derivatives, styrylanthracene derivatives,fluorenone derivatives, hydrazone derivatives, stilbene derivatives,silazane derivatives, aromatic tertiary amine compounds, styrylaminecompounds, aromatic dimethylidine compounds, phthalocyanine compounds,porphyrin compounds, organosilane derivatives, carbon, and the like.

An electron-accepting dopant may be introduced into the hole injectionlayer or the hole transport layer in the organic EL element of thepresent invention. As the electron-accepting dopant to be introducedinto the hole injection layer or the hole transport layer, either of aninorganic compound or an organic compound may be used as long as thecompound has electron accepting property and a function for oxidizing anorganic compound.

Specifically, the inorganic compound includes metal halides such asferric chloride, aluminum chloride, gallium chloride, indium chloride,antimony pentachloride and the like, and metal oxides such as vanadiumpentaoxide, molybdenum trioxide and the like.

In case of employing the organic compounds, compounds having asubstituent such as a nitro group, a halogen, a cyano group, atrifluoromethyl group or the like; quinone compounds; acid anhydridecompounds; fullerenes; and the like may be preferably applied.

Specific examples hole injection and hole transport materials includecompounds described in patent documents such as JP-A Nos. 6-212153,11-111463, 11-251067, 2000-196140, 2000-286054, 2000-315580,2001-102175, 2001-160493, 2002-252085, 2002-56985, 2003-157981,2003-217862, 2003-229278, 2004-342614, 2005-72012, 2005-166637,2005-209643 and the like.

Specific examples of hole injection and hole transport materials includethe organic compounds: hexacyanobutadiene, hexacyanobenzene,tetracyanoethylene, tetracyanoquinodimethane,tetrafluorotetracyanoquinodimethane, p-fluoranil, p-chloranil,p-bromanil, p-benzoquinone, 2,6-dichlorobenzoquinone,2,5-dichlorobenzoquinone, 1,2,4,5-tetracyanobenzene,1,4-dicyanotetrafluorobenzene, 2,3-dichloro-5,6-dicyanobenzoquinone,p-dinitrobenzene, m-dinitrobenzene, o-dinitrobenzene,1,4-naphthoquinone, 2,3-dichloronaphthoquinone, 1,3-dinitronaphthalene,1,5-dinitronaphthalene, 9,10-anthraquinone, 1,3,6,8-tetranitrocarbazole,2,4,7-trinitro-9-fluorenone, 2,3,5,6-tetracyanopyridine and fullereneC₆₀. Among these, hexacyanobutadiene, hexacyanobenzene,tetracyanoethylene, tetracyanoquinodimethane,tetrafluorotetracyanoquinodimethane, p-fluoranil, p-chloranil,p-bromanil, 2,6-dichlorobenzoquinone, 2,5-dichlorobenzoquinone,2,3-dichloronaphthoquinone, 1,2,4,5-tetracyanobenzene,2,3-dichloro-5,6-dicyanobenzoquinone and 2,3,5,6-tetracyanopyridine aremore preferable, and tetrafluorotetracyanoquinodimethane.

As one or more electron-accepting dopants may be introduced into thehole injection layer or the hole transport layer in the organic ELelement of the present invention, these electron-accepting dopants maybe used alone or in combinations of two or more. Although precise amountof these electron-accepting dopants used will depend on the type ofmaterial, about 0.01% by weight to about 50% by weight of the totalweight of the hole transport layer or the hole injection layer ispreferred. In some embodiments, the amount of these electron-acceptingdopants range from about 0.05% by weight to about 20% by weight of thetotal weight of the hole transport layer or the hole injection layer. Insome embodiments, the amount of these electron-accepting dopants rangefrom about 0.1% by weight to about 10% by weight of the total weight ofthe hole transport layer or the hole injection layer.

In some embodiments, a thickness of the hole injection layer and athickness of the hole transport layer are each preferably about 500 nmor less in view of decreasing driving voltage or optimizing for opticaloutcoupling. In some embodiments, the thickness of the hole transportlayer is preferably from about 1 nm to about 500 nm. In someembodiments, the thickness of the hole transport layer is preferablyfrom about 5 nm to about 50 nm. In some embodiments, the thickness ofthe hole transport layer is preferably from about 10 nm to about 40 nm.In some embodiments, the thickness of the hole injection layer ispreferably from about 0.1 nm to about 500 nm. In some embodiments, thethickness of the hole injection layer is preferably from about 0.5 nm toabout 300 nm. In some embodiments, the thickness of the hole injectionlayer is preferably from about 1 nm to about 200 nm.

The hole injection layer and the hole transport layer may be composed ofa monolayer structure comprising one or two or more of theabove-mentioned materials, or a multilayer structure composed of plurallayers of a homogeneous composition or a heterogeneous composition.

F. Electron Injection Layer and Electron Transport Layer

The electron injection layer and the electron transport layer are layershaving functions for receiving electrons from a cathode or a cathodeside, and transporting electrons to the light emitting layer. Anelectron injection material or an electron transporting material usedfor these layers may be a low molecular compound or a high molecularcompound. Specific examples of the materials suitable for use inelectron injection and electron transport layers include, but are notlimited to, pyridine derivatives, quinoline derivatives, pyrimidinederivatives, pyrazine derivatives, phthalazine derivatives,phenanthroline derivatives, triazine derivatives, triazole derivatives,oxazole derivatives, oxadiazole derivatives, imidazole derivatives,fluorenone derivatives, anthraquinodimethane derivatives, anthronederivatives, diphenylquinone derivatives, thiopyrandioxide derivatives,carbodiimide derivatives, fluorenylidenemethane derivatives,distyrylpyrazine derivatives, aromacyclic tetracarboxylic anhydrides ofperylene, naphthalene or the like, phthalocyanine derivatives, metalcomplexes represented by metal complexes of 8-quinolinol derivatives,metal phthalocyanine, and metal complexes containing benzoxazole, orbenzothiazole as the ligand, organic silane derivatives exemplified bysilole, and the like.

The electron injection layer or the electron transport layer may containan electron donating dopant. Suitable electron donating dopant for usein the electron injection layer or the electron transport layer, includeany suitable material that may be used as long as it has anelectron-donating property and a property for reducing an organiccompound. Specific examples of electron donating dopants include analkaline metal such as Li, an alkaline earth metal such as Mg, atransition metal including a rare-earth metal, and a reducing organiccompound. Other examples of metal donating dopants include, metalshaving a work function of 4.2 V or less, for example, Li, Na, K, Be, Mg,Ca, Sr, Ba, Y, Cs, La, Sm, Gd, Yb, and the like. Specific examples ofthe reducing organic compounds include nitrogen-containing compounds,sulfur-containing compounds, phosphorus-containing compounds, and thelike.

The electron donating dopants may be used alone or in combinations oftwo or more. In some embodiments, an electron donating dopant iscontained in the electron injection layer or the electron transportlayer in an amount ranging from about 0.1% by weight to about 99% byweight of the total weight of the electron transport layer material orthe electron injecting layer mater. In some embodiments, an electrondonating dopant is contained in the electron injection layer or theelectron transport layer in an amount ranging from about 1.0% by weightto about 80% by weight of the total weight of the electron transportlayer material or the electron injecting layer material. In someembodiments, an electron donating dopant is contained in the electroninjection layer or the electron transport layer in an amount rangingfrom about 2.0% by weight to about 70% by weight of the total weight ofthe electron transport layer material or the electron injecting layermaterial.

A thickness of the electron injection layer and a thickness of theelectron transport layer are each preferably 500 nm or less in view ofdecrease in driving voltage. The thickness of the electron transportlayer is preferably from 1 nm to 500 nm, more preferably from 5 nm to200 nm, and even more preferably from 10 nm to 100 nm. A thickness ofthe electron injection layer is preferably from 0.1 nm to 200 nm, morepreferably from 0.2 nm to 100 nm, and even more preferably from 0.5 nmto 50 nm.

The electron injection layer and the electron-transport may be composedof a monolayer structure comprising one or two or more of theabove-mentioned materials, or a multilayer structure composed of plurallayers of a homogeneous composition or a heterogeneous composition.

Combination with Other Materials

The materials described herein as useful for a particular layer in anorganic light emitting device may be used in combination with a widevariety of other materials present in the device. For example, emissivedopants disclosed herein may be used in conjunction with a wide varietyof hosts, transport layers, blocking layers, injection layers,electrodes and other layers that may be present. The materials describedor referred to below are non-limiting examples of materials that may beuseful in combination with the compounds disclosed herein, and one ofskill in the art can readily consult the literature to identify othermaterials that may be useful in combination.

HIL/HTL:

A hole injecting/transporting material to be used in the presentinvention is not particularly limited, and any compound may be used aslong as the compound is typically used as a hole injecting/transportingmaterial. Examples of the material include, but are not limited to: aphthalocyanine or porphyrin derivative; an aromatic amine derivative; anindolocarbazole derivative; a polymer containing fluorohydrocarbon; apolymer with conductivity dopants; a conducting polymer, such asPEDOT/PSS; a self-assembly monomer derived from compounds such asphosphonic acid and silane derivatives; a metal oxide derivative, suchas MoO_(x); a p-type semiconducting organic compound, such as1,4,5,8,9,12-Hexaazatriphenylenehexacarbonitrile; a metal complex, and across-linkable compound.

Examples of aromatic amine derivatives used in HIL or HTL include, butare not limited to the following general structures:

Each of Ar¹ to Ar⁹ is selected from the group consisting of aromatichydrocarbon cyclic compounds such as benzene, biphenyl, triphenyl,triphenylene, naphthalene, anthracene, phenalene, phenanthrene,fluorene, pyrene, chrysene, perylene, and azulene; the group consistingof aromatic heterocyclic compounds such as dibenzothiophene,dibenzofuran, dibenzoselenophene, furan, thiophene, benzofuran,benzothiophene, benzoselenophene, carbazole, indolocarbazole,pyridylindole, pyrrolodipyridine, pyrazole, imidazole, triazole,oxazole, thiazole, oxadiazole, oxatriazole, dioxazole, thiadiazole,pyridine, pyridazine, pyrimidine, pyrazine, triazine, oxazine,oxathiazine, oxadiazine, indole, benzimidazole, indazole, indoxazine,benzoxazole, benzisoxazole, benzothiazole, quinoline, isoquinoline,cinnoline, quinazoline, quinoxaline, naphthyridine, phthalazine,pteridine, xanthene, acridine, phenazine, phenothiazine, phenoxazine,benzofuropyridine, furodipyridine, benzothienopyridine,thienodipyridine, benzoselenophenopyridine, and selenophenodipyridine;and the group consisting of 2 to 10 cyclic structural units which aregroups of the same type or different types selected from the aromatichydrocarbon cyclic group and the aromatic heterocyclic group and arebonded to each other directly or via at least one of oxygen atom,nitrogen atom, sulfur atom, silicon atom, phosphorus atom, boron atom,chain structural unit and the aliphatic cyclic group. Wherein each Ar isfurther substituted by a substituent selected from the group consistingof hydrogen, deuterium, halide, alkyl, cycloalkyl, heteroalkyl,arylalkyl, alkoxy, aryloxy, amino, silyl, alkenyl, cycloalkenyl,heteroalkenyl, alkynyl, aryl, heteroaryl, acyl, carbonyl, carboxylicacids, ester, nitrile, isonitrile, sulfanyl, sulfinyl, sulfonyl,phosphino, and combinations thereof.

In one aspect, Ar¹ to Ar⁹ is independently selected from the groupconsisting of:

wherein k is an integer from 1 to 20; X¹⁰¹ to X¹⁰⁸ is C (including CH)or N; Z¹⁰¹ is NAr¹, O, or S; Ar¹ has the same group defined above.

Examples of metal complexes used in HIL or HTL include, but are notlimited to the following general formula:

wherein Met is a metal, which can have an atomic weight greater than 40;(Y¹⁰¹-Y¹⁰²) is a bidentate ligand, Y¹⁰¹ and Y¹⁰² are independentlyselected from C, N, O, P, and S; L¹⁰¹ is an ancillary ligand; k′ is aninteger value from 1 to the maximum number of ligands that may beattached to the metal; and k′+k″ is the maximum number of ligands thatmay be attached to the metal.

In one aspect, (Y¹⁰¹-Y¹⁰²) is a 2-phenylpyridine derivative. In anotheraspect, (Y¹⁰¹-Y¹⁰²) is a carbene ligand. In another aspect, Met isselected from Ir, Pt, Os, and Zn. In a further aspect, the metal complexhas a smallest oxidation potential in solution vs. Fc⁺/Fc couple lessthan about 0.6 V.

Non-limiting examples of the HIL and HTL materials that may be used inan OLED in combination with materials disclosed herein are exemplifiedbelow together with references that disclose those materials:CN102702075, DE102012005215, EP01624500, EP01698613, EP01806334,EP01930964, EP01972613, EP01997799, EP02011790, EP02055700, EP02055701,EP1725079, EP2085382, EP2660300, EP650955, JP07-073529, JP2005112765,JP2007091719, JP2008021687, JP2014-009196, KR20110088898, KR20130077473,TW201139402, U.S. Ser. No. 06/517,957, US20020158242, US20030162053,US20050123751, US20060182993, US20060240279, US20070145888,US20070181874, US20070278938, US20080014464, US20080091025,US20080106190, US20080124572, US20080145707, US20080220265,US20080233434, US20080303417, US2008107919, US20090115320,US20090167161, US2009066235, US2011007385, US20110163302, US2011240968,US2011278551, US2012205642, US2013241401, US20140117329, US2014183517,U.S. Pat. No. 5,061,569, U.S. Pat. No. 5,639,914, WO05075451,WO07125714, WO08023550, WO08023759, WO2009145016, WO2010061824,WO2011075644, WO2012177006, WO2013018530, WO2013039073, WO2013087142,WO2013118812, WO2013120577, WO2013157367, WO2013175747, WO2014002873,WO2014015935, WO2014015937, WO2014030872, WO2014030921, WO2014034791,WO2014104514, WO2014157018.

EBL:

An electron blocking layer (EBL) may be used to reduce the number ofelectrons and/or excitons that leave the emissive layer. The presence ofsuch a blocking layer in a device may result in substantially higherefficiencies, and or longer lifetime, as compared to a similar devicelacking a blocking layer. Also, a blocking layer may be used to confineemission to a desired region of an OLED. In some embodiments, the EBLmaterial has a higher LUMO (closer to the vacuum level) and or highertriplet energy than the emitter closest to the EBL interface. In someembodiments, the EBL material has a higher LUMO (closer to the vacuumlevel) and or higher triplet energy than one or more of the hostsclosest to the EBL interface. In one aspect, compound used in EBLcontains the same molecule or the same functional groups used as one ofthe hosts described below.

Host:

The light emitting layer of the organic EL device of the presentinvention preferably contains at least a metal complex as light emittingmaterial, and may contain a host material using the metal complex as adopant material. In some embodiments, two or more hosts are preferred.In some embodiments, the hosts used maybe a) bipolar, b) electrontransporting, c) hole transporting or d) wide band gap materials thatplay little role in charge transport. Examples of the host material arenot particularly limited, and any metal complexes or organic compoundsmay be used as long as the triplet energy of the host is larger thanthat of the dopant. While the Table below categorizes host materials aspreferred for devices that emit various colors, any host material may beused with any dopant so long as the triplet criteria is satisfied.

Examples of metal complexes used as host are preferred to have thefollowing general formula:

wherein Met is a metal; (Y¹⁰³-Y¹⁰⁴) is a bidentate ligand, Y¹⁰³ and Y¹⁰⁴are independently selected from C, N, O, P, and S; L¹⁰¹ is an anotherligand; k′ is an integer value from 1 to the maximum number of ligandsthat may be attached to the metal; and k′+k″ is the maximum number ofligands that may be attached to the metal.

In one aspect, the metal complexes are:

wherein (O—N) is a bidentate ligand, having metal coordinated to atoms Oand N.

In another aspect, Met is selected from Ir and Pt. In a further aspect,(Y¹⁰³-Y¹⁰⁴) is a carbene ligand.

Examples of organic compounds used as host are selected from the groupconsisting of aromatic hydrocarbon cyclic compounds such as benzene,biphenyl, triphenyl, triphenylene, naphthalene, anthracene, phenalene,phenanthrene, fluorene, pyrene, chrysene, perylene, and azulene; thegroup consisting of aromatic heterocyclic compounds such asdibenzothiophene, dibenzofuran, dibenzoselenophene, furan, thiophene,benzofuran, benzothiophene, benzoselenophene, carbazole,indolocarbazole, pyridylindole, pyrrolodipyridine, pyrazole, imidazole,triazole, oxazole, thiazole, oxadiazole, oxatriazole, dioxazole,thiadiazole, pyridine, pyridazine, pyrimidine, pyrazine, triazine,oxazine, oxathiazine, oxadiazine, indole, benzimidazole, indazole,indoxazine, benzoxazole, benzisoxazole, benzothiazole, quinoline,isoquinoline, cinnoline, quinazoline, quinoxaline, naphthyridine,phthalazine, pteridine, xanthene, acridine, phenazine, phenothiazine,phenoxazine, benzofuropyridine, furodipyridine, benzothienopyridine,thienodipyridine, benzoselenophenopyridine, and selenophenodipyridine;and the group consisting of 2 to 10 cyclic structural units which aregroups of the same type or different types selected from the aromatichydrocarbon cyclic group and the aromatic heterocyclic group and arebonded to each other directly or via at least one of oxygen atom,nitrogen atom, sulfur atom, silicon atom, phosphorus atom, boron atom,chain structural unit and the aliphatic cyclic group. Wherein each groupis further substituted by a substituent selected from the groupconsisting of hydrogen, deuterium, halide, alkyl, cycloalkyl,heteroalkyl, arylalkyl, alkoxy, aryloxy, amino, silyl, alkenyl,cycloalkenyl, heteroalkenyl, alkynyl, aryl, heteroaryl, acyl, carbonyl,carboxylic acids, ester, nitrile, isonitrile, sulfanyl, sulfinyl,sulfonyl, phosphino, and combinations thereof.

In one aspect, the host compound contains at least one of the followinggroups in the molecule:

wherein R¹⁰¹ to R¹⁰⁷ is independently selected from the group consistingof hydrogen, deuterium, halide, alkyl, cycloalkyl, heteroalkyl,arylalkyl, alkoxy, aryloxy, amino, silyl, alkenyl, cycloalkenyl,heteroalkenyl, alkynyl, aryl, heteroaryl, acyl, carbonyl, carboxylicacids, ester, nitrile, isonitrile, sulfanyl, sulfinyl, sulfonyl,phosphino, and combinations thereof, when it is aryl or heteroaryl, ithas the similar definition as Ar's mentioned above. k is an integer from0 to 20 or 1 to 20; k′″ is an integer from 0 to 20. X¹⁰¹ to X¹⁰⁸ isselected from C (including CH) or N.Z¹⁰¹ and Z¹⁰² is selected from NR¹⁰¹, O, or S.

Non-limiting examples of the host materials that may be used in an OLEDin combination with materials disclosed herein are exemplified belowtogether with references that disclose those materials: EP2034538,EP2034538A, EP2757608, JP2007254297, KR20100079458, KR20120088644,KR20120129733, KR20130115564, TW201329200, US20030175553, US20050238919,US20060280965, US20090017330, US20090030202, US20090167162,US20090302743, US20090309488, US20100012931, US20100084966,US20100187984, US2010187984, US2012075273, US2012126221, US2013009543,US2013105787, US2013175519, US2014001446, US20140183503, US20140225088,US2014034914, U.S. Pat. No. 7,154,114, WO2001039234, WO2004093207,WO2005014551, WO2005089025, WO2006072002, WO2006114966, WO2007063754,WO2008056746, WO2009003898, WO2009021126, WO2009063833, WO2009066778,WO2009066779, WO2009086028, WO2010056066, WO2010107244, WO2011081423,WO2011081431, WO2011086863, WO2012128298, WO2012133644, WO2012133649,WO2013024872, WO2013035275, WO2013081315, WO2013191404, WO2014142472,

Additional Emitters

One or more additional emitter dopants may be used in conjunction withthe compound of the present disclosure. Examples of the additionalemitter dopants are not particularly limited, and any compounds may beused as long as the compounds are typically used as emitter materials.Examples of suitable emitter materials include, but are not limited to,compounds which can produce emissions via phosphorescence, fluorescence,thermally activated delayed fluorescence, i.e., TADF (also referred toas E-type delayed fluorescence), triplet-triplet annihilation, orcombinations of these processes.

Non-limiting examples of the emitter materials that may be used in anOLED in combination with materials disclosed herein are exemplifiedbelow together with references that disclose those materials:CN103694277, CN1696137, EB01238981, EP01239526, EP01961743, EP1239526,EP1244155, EP1642951, EP1647554, EP1841834, EP1841834B, EP2062907,EP2730583, JP2012074444, JP2013110263, JP4478555, KR1020090133652,KR20120032054, KR20130043460, TW201332980, U.S. Ser. No. 06/699,599,U.S. Ser. No. 06/916,554, US20010019782, US20020034656, US20030068526,US20030072964, US20030138657, US20050123788, US20050244673,US2005123791, US2005260449, US20060008670, US20060065890, US20060127696,US20060134459, US20060134462, US20060202194, US20060251923,US20070034863, US20070087321, US20070103060, US20070111026,US20070190359, US20070231600, US2007034863, US2007104979, US2007104980,US2007138437, US2007224450, US2007278936, US20080020237, US20080233410,US20080261076, US20080297033, US200805851, US2008161567, US2008210930,US20090039776, US20090108737, US20090115322, US20090179555,US2009085476, US2009104472, US20100090591, US20100148663, US20100244004,US20100295032, US2010102716, US2010105902, US2010244004, US2010270916,US20110057559, US20110108822, US20110204333, US2011215710, US2011227049,US2011285275, US2012292601, US20130146848, US2013033172, US2013165653,US2013181190, US2013334521, US20140246656, US2014103305, U.S. Pat. No.6,303,238, U.S. Pat. No. 6,413,656, U.S. Pat. No. 6,653,654, U.S. Pat.No. 6,670,645, U.S. Pat. No. 6,687,266, U.S. Pat. No. 6,835,469, U.S.Pat. No. 6,921,915, U.S. Pat. No. 7,279,704, U.S. Pat. No. 7,332,232,U.S. Pat. No. 7,378,162, U.S. Pat. No. 7,534,505, U.S. Pat. No.7,675,228, U.S. Pat. No. 7,728,137, U.S. Pat. No. 7,740,957, U.S. Pat.No. 7,759,489, U.S. Pat. No. 7,951,947, U.S. Pat. No. 8,067,099, U.S.Pat. No. 8,592,586, U.S. Pat. No. 8,871,361, WO06081973, WO06121811,WO07018067, WO07108362, WO07115970, WO07115981, WO08035571,WO2002015645, WO2003040257, WO2005019373, WO2006056418, WO2008054584,WO2008078800, WO2008096609, WO2008101842, WO2009000673, WO2009050281,WO2009100991, WO2010028151, WO2010054731, WO2010086089, WO2010118029,WO2011044988, WO2011051404, WO2011107491, WO2012020327, WO2012163471,WO2013094620, WO2013107487, WO2013174471, WO2014007565, WO2014008982,WO2014023377, WO2014024131, WO2014031977, WO2014038456, WO2014112450.

HBL:

A hole blocking layer (HBL) may be used to reduce the number of holesand/or excitons that leave the emissive layer. The presence of such ablocking layer in a device may result in substantially higherefficiencies and/or longer lifetime as compared to a similar devicelacking a blocking layer. Also, a blocking layer may be used to confineemission to a desired region of an OLED. In some embodiments, the HBLmaterial has a lower HOMO and or higher triplet energy than the emitterclosest to the HBL interface.

In one aspect, compound used in HBL contains the same molecule or thesame functional groups used as host described above.

In another aspect, compound used in HBL contains at least one of thefollowing groups in the molecule:

wherein k is an integer from 1 to 20; L¹⁰¹ is an another ligand, k′ isan integer from 1 to 3.

ETL:

Electron transport layer (ETL) may include a material capable oftransporting electrons. Electron transport layer may be intrinsic(undoped), or doped. Doping may be used to enhance conductivity.Examples of the ETL material are not particularly limited, and any metalcomplexes or organic compounds may be used as long as they are typicallyused to transport electrons.

In one aspect, compound used in ETL contains at least one of thefollowing groups in the molecule:

wherein R¹⁰¹ is selected from the group consisting of hydrogen,deuterium, halide, alkyl, cycloalkyl, heteroalkyl, arylalkyl, alkoxy,aryloxy, amino, silyl, alkenyl, cycloalkenyl, heteroalkenyl, alkynyl,aryl, heteroaryl, acyl, carbonyl, carboxylic acids, ester, nitrile,isonitrile, sulfanyl, sulfinyl, sulfonyl, phosphino, and combinationsthereof, when it is aryl or heteroaryl, it has the similar definition asAr's mentioned above. Ar¹ to Ar³ has the similar definition as Ar'smentioned above. k is an integer from 1 to 20. X¹⁰¹ to X¹⁰⁸ is selectedfrom C (including CH) or N.

In another aspect, the metal complexes used in ETL include, but are notlimited to the following general formula:

wherein (O—N) or (N—N) is a bidentate ligand, having metal coordinatedto atoms O, N or N, N; L¹⁰¹ is another ligand; k′ is an integer valuefrom 1 to the maximum number of ligands that may be attached to themetal.

Non-limiting examples of the ETL materials that may be used in an OLEDin combination with materials disclosed herein are exemplified belowtogether with references that disclose those materials: CN103508940,EP01602648, EP01734038, EP01956007, JP2004-022334, JP2005149918,JP2005-268199, KR0117693, KR20130108183, US20040036077, US20070104977,US2007018155, US20090101870, US20090115316, US20090140637,US20090179554, US2009218940, US2010108990, US2011156017, US2011210320,US2012193612, US2012214993, US2014014925, US2014014927, US20140284580,U.S. Pat. No. 6,656,612, U.S. Pat. No. 8,415,031, WO2003060956,WO2007111263, WO2009148269, WO2010067894, WO2010072300, WO2011074770,WO2011105373, WO2013079217, WO2013145667, WO2013180376, WO2014104499,WO2014104535,

Charge Generation Layer (CGL):

In tandem or stacked OLEDs, the CGL plays an essential role in theperformance, which is composed of an n-doped layer and a p-doped layerfor injection of electrons and holes, respectively. Electrons and holesare supplied from the CGL and electrodes. The consumed electrons andholes in the CGL are refilled by the electrons and holes injected fromthe cathode and anode, respectively; then, the bipolar currents reach asteady state gradually. Typical CGL materials include n and pconductivity dopants used in the transport layers.

In any above-mentioned compounds used in each layer of the OLED device,the hydrogen atoms can be partially or fully deuterated. Thus, anyspecifically listed substituent, such as, without limitation, methyl,phenyl, pyridyl, etc. encompasses undeuterated, partially deuterated,and fully deuterated versions thereof. Similarly, classes ofsubstituents such as, without limitation, alkyl, aryl, cycloalkyl,heteroaryl, etc. also encompass undeuterated, partially deuterated, andfully deuterated versions thereof.

The invention is explained in greater detail by the following examples,without wishing to restrict it thereby. The person skilled in the artwill be able to produce further electronic devices on the basis of thedescriptions without inventive step and will thus be able to carry outthe invention throughout the range claimed.

EXAMPLES

The following syntheses are carried out, unless indicated otherwise, indried solvents under a protective-gas atmosphere. The metal complexesare additionally handled with exclusion of light. The solvents andreagents can be purchased, for example, from Sigma-ALDRICH or ABCR.

Example 1: Synthesis of3,4-dihydrodibenzo[b,ij]imidazo[2,1,5-de]quinolizine was Prepared inAccordance with Scheme 1

A. Synthesis of 4-chlorobutanal

A solution of oxalyl chloride (22.54 ml, 263 mmol) in DCM (400 ml) wascooled in an ^(i)PrOH/CO₂ bath. DMSO (37.3 ml, 525 mmol) was slowly viasyringe and stirred cold for 1 hour. A solution of 4-chlorobutan-1-ol(19 g, 175 mmol) in 50 mL DCM was added dropwise. The col mixture wasstirred for one hour, then, triethylamine (110 ml, 788 mmol) was slowlyadded. The suspension was stirred cold for 30 minutes, then allowed towarm to room temperature. The reaction was quenched with water,acidified and organics separated. Solvent removal followed bydistillation yielded the product as a colorless oil, 8 g.

B. Synthesis of 2-bromo-4-chlorobutanal

4-chlorobutanal (7.939 g, 74.5 mmol) was dissolved in DCM (300 ml) andcooled in an ice bath. A solution of dibromine (4.00 ml, 78 mmol) in DCM(50 ml) was added over about 1 hr. After addition the red solution wasstirred cold for 30 minutes, then warmed slowly to room temperature andstirred one more hour. Water was added, the organics were separated, anddrying and solvent removal yielded the crude product as a pale yellowoil, 1.57 g (80%).

C. Synthesis of 4-bromophenanthridin-6-amine

2,6-dibromoaniline (15.33 g, 61.1 mmol),2-(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-yl)benzonitrile (7.0 g, 30.6mmol), and potassium phosphate monohydrate (21.11 g, 92 mmol) werecombined in dioxane (120 ml) and water (7.49 ml). The mixture wasdegassed, then added (dppf)PdCl₂ complex with DCM (0.749 g, 0.917 mmol)was added and the mixture was refluxed for 4 hours. The black mixturewas partitioned between EtOAc and water/brine. The organic layer waswashed with brine, dried, and solvent was removed. Dissolution in 500 mLEtOAc followed by elution through a silica plug using EtOAc and solventremoval yielded an orange residue that was purified by columnchromatography to yield the product as a yellow/orange solid, 5.86 g,70%.

D. Synthesis of 5-bromo-3-(2-chloroethyl)imidazo[1,2-f]phenanthridine

4-bromophenanthridin-6-amine (5.86, 21.46 mmol), 2-bromo-4-chlorobutanal(5.36 g, 28.9 mmol), and sodium bicarbonate (3.60 g, 42.9 mmol) werecombined in 2-propanol (102 ml) and water (5.11 ml). The suspension wasstirred at room temperature for 4 hours, then at reflux for 16 hours.Solvent was removed under vacuum and the residue coated on celite.Column chromatography yielded a mixture of the product and startingamidine, which was treated with excess acetyl chloride and triethylaminein DCM. After workup the desired product was extracted from theacetamide by repeated extraction into heptanes, yielding 3.93 g ofyellow, tacky residue (51%).

E. Synthesis of 3,4-dihydrodibenzo[b,ij]imidazo[2,1,5-de]quinolizine

5-bromo-3-((2-chloroethyl)imidazo[1,2-f]phenanthridine (3.93 g, 10.93mmol) was dissolved in THF (200 ml), cooled in an ice bath, andisopropylmagnesium chloride solution in THF (2.0M, 6.01 ml, 12.02 mmol)was slowly added. The solution was stirred for 30 minutes cold, thenwarmed to room temperature and stirred for 2 more hours. The reactionwas quenched, extracted into DCM, and the reaction product was purifiedusing column chromatography to yield 1.90 g of a pale beige, crystallinesolid (71%).

An X-ray structure of3,4-dihydrodibenzo[b,ij]imidazo[2,1,5-de]quinolizine is shown in FIG. 5.The crystal structure of3,4-dihydrodibenzo[b,ij]imidazo[2,1,5-de]quinolizine may be defined byone or more of the characteristics listed in the following table.

Formula C₁₇H₁₂N₂ Data/restr./param. 2107/0/173 MW 244.29 T [K] 100(1)   Crystal system Orthorhombic ρ_(cald) [g cm⁻³] 1.410 Space group P2₁2₁2₁μ_(calcd) [mm⁻¹] 0.084 Color Colorless Total reflections 22768      a[Å] 6.6974(5) Z 4    b [Å] 11.0502(8) F(000) 512     c [Å] 15.5459(10)T_(min)/T_(max) 0.894 α [°] 90 Cryst. Size [mm³] 0.42 × 0.22 × 0.08 β[°] 90 R₁ [I>2σ(I)]^(a)  0.0405 γ [°] 90 wR₂ (all data)^(a)  0.1173 V[Å³] 1150.52(14) GOF^(a) 1.075 ^(a)R₁ = Σ||F_(o)| − |F_(c)||/Σ|F_(o)|;wR₂ = [Σ[w(F_(o) ² − F_(c) ²)²]/Σ[w(F_(o) ²)²]]^(1/2); GOF = [Σw(|F_(o)|− |F_(c)|)²/(n − m)]^(1/2)

?!

Example 2: Synthesis of4,4-dimethyl-3,4-dihydro-1,2a1-diaza-4-silabenzo[fg]aceanthrylene and3,3-dimethyl-3,4-dihydro-1,2a1-diaza-3-silabenzo[fg]aceanthrylene

The ligands above are prepared in accordance with Scheme 2 below.

A. Synthesis of 5-bromoimidazo[1,2-f]phenanthridine

4-bromophenanthridin-6-amine (4.0 g, 14.7 mmol) was dissolved in 100 mLof iPrOH.

Chloroacetaldehyde (50% in water, 3.6 g, 22 mmol, 1.5 equiv.) was added,followed by NaHCO₃ (2.5 g, 2 equiv.), and the mixture was refluxed for 2hours, then cooled in an ice bath. The tan solid was filtered off,washing with MeOH. The receiving flask was changed and the solid waswashed with water, resulting in clean, off-white product, 3.2 g. Theaqueous washes were extracted with EtOAc and these extracts werecombined with the alcoholic washes from the initial filtration. Solventwas removed to yield 1.3 g of an orange solid which was recrystallizedfrom EtOAc, yielding more clean product as tan needles, 0.46 g. Totalyield: 3.5 g (80%).

B. Synthesis of 3,5-dibromoimidazo[1,2-f]phenanthridine

Dissolved 5-bromoimidazo[1,2-f]phenanthridine (2.0 g, 6.73 mmol) in DMF(125 ml), then added a solution of NBS (1.318 g, 7.40 mmol) in 10 mL ofDMF slowly under nitrogen. After stirring for 3 hours at roomtemperature, then gentle heating for 16 hours, the reaction mixture waspartitioned between 300 mL of water and EtOAc. The aqueous layer wasfurther extracted with EtOAc, the organics washed with water, and theproduct was isolated by column chromatography as a pale yellow solid,1.99 g (79%).

C. Synthesis of5-bromo-3-((chloromethyl)dimethylsilyl)imidazo[1,2-f]phenanthridine

3,5-dibromoimidazo[1,2-f]phenanthridine (0.48 g, 1.28 mmol) andchloro(chloromethyl)dimethylsilane (0.17 ml, 1.28 mmol) were dissolvedin THF (25 ml) and cooled in iPrOH/CO₂ bath. Butyllithium solution inhexanes (2.5 M, 0.51 ml, 1.28 mmol) was added slowly, the mixture wasstirred cold for 30 minutes, then allowed to warm to room temperature.Brine was added to quench the reaction, the organics were extracted intoEtOAc and purified by column chromatography to yield the product as acolorless, tacky residue, 0.16 g (31%).

D. Synthesis of4,4-dimethyl-3,4-dihydro-1,2a1-diaza-4-silabenzo[fg]aceanthrylene and3,3-dimethyl-3,4-dihydro-1,2a1-diaza-3-silabenzo[fg]aceanthrylene

5-bromo-3-((chloromethyl)dimethylsilyl)imidazo[1,2-f]phenanthridine(0.13 g, 0.322 mmol) was dissolved in THF (25 ml) and cooled in an icebath. Isopropylmagnesium chloride solution in THF (2.0 M, 0.18 ml, 0.36mmol) was added slowly, then warmed to room temperature. The reactionwas quenched with brine, organics were extracted with DCM, and themixture chromatographed to yield 16 mg of4,4-dimethyl-3,4-dihydro-1,2a1-diaza-4-silabenzo[fg]aceanthrylene as atacky residue (17%), and 33 mg of3,3-dimethyl-3,4-dihydro-1,2a1-diaza-3-silabenzo[fg]aceanthrylene as acrystalline solid (36%).

Furthermore, all organic materials used in this example weresublimation-purified and analyzed by high-performance liquidchromatography (Tosoh TSKgel ODS-100Z), and materials having 99.9% orhigher of an absorption intensity area ratio at 254 nm were used.

An X-ray structure of3,3-dimethyl-3,4-dihydro-1,2a1-diaza-3-silabenzo[fg]aceanthrylene isshown in FIG. 6. The crystal structure of3,3-dimethyl-3,4-dihydro-1,2a1-diaza-3-silabenzo[fg]aceanthrylene may bedefined by one or more of the characteristics listed in the followingtable.

Formula C₁₈H₁₆N₂Si Data/restr./param. 5211/0/384 MW 288.42 T [K]100(1)    Crystal system Triclinic ρ_(cald) [g cm⁻³] 1.341 Space groupP-1 μ_(calcd) [mm⁻¹] 0.159 Color Colorless Total reflections 54823     a [Å] 9.1888(8) Z 4    b [Å] 12.5217(11) F(000) 608     c [Å]12.5428(12) T_(min)/T_(max) 0.954 α [°] 82.769(4) Cryst. Size [mm³] 0.28× 0.18 × 0.15 β [°] 89.062(4) R₁ [I>2σ(I)]^(a)  0.0324 γ [°] 86.121(2)wR₂ (all data)^(a)  0.0892 V [Å³] 1428.4(2) GOF^(a) 1.055 ^(a)R₁ =Σ||F_(o)| − |F_(c)||/Σ|F_(o)|; wR₂ = [Σ[w(F_(o) ² − F_(c) ²)²]/Σ[w(F_(o)²)²]]^(1/2); GOF = [Σw(|F_(o)| − |F_(c)|)²/(n − m)]^(1/2)

Example 3: Synthesis of platinum(II) complex of6-isopropyl-10-((9-(4-isopropylpyridin-2-yl)-9H-carbazol-2-yl)oxy)-3,4-dihydrodibenzo[b,ij]imidazo[2,1,5-de]quinolizine

A. Synthesis of 2-Bromo-5-methoxybenzonitrile

A mixture of 2-bromo-5-methoxybenzaldehyde (100 g, 0.47 mol, 1 equiv),hydroxylamine hydrochloride (64.8 g, 0.93 mol, 2 equiv), sodium acetate(76.42 g, 0.93 mol, 2 equiv) and glacial acetic acid (500 mL) wasrefluxed for 16 hours. The acetic acid was removed under reducedpressure and the residue was extracted with dichloromethane (˜400 mL).The organic layer was washed with saturated brine (3×200 mL), dried oversodium sulfate and concentrated under reduced pressure. The resultingresidue was triturated with heptanes (50 mL) and solids washed withadditional heptanes (2×50 mL) to give the desired product as a whitepowder (82.6 g, 86% yield).

B. Synthesis of5-Methoxy-2-(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-yl)benzonitrile

A mixture of 2-bromo-5-methoxybenzonitrile (82.6 g, 0.39 mol, 1 equiv),bis(pinacolato)diboron (109.1 g, 0.43 mol, 1.1 equiv) and potassiumacetate (115.3 g, 1.17 mol, 3 equiv) in a mixture of 1,4-dioxane (400mL) and DMSO (40 mL) was sparged with nitrogen for 1 hour. Pd(dppf)Cl₂(7.13 g, 5 mol %) was added and reaction mixture was gently heated at60° C. for 2 hours then refluxed for 16 hours. The mixture was filteredthrough celite and the solids isolated from the filtrates were washedwith isopropanol and heptanes to give the desired product as anoff-white solid (57.41 g, 57% yield). Additional product (˜10 g) wasisolated from the filtrates.

C. Synthesis of 4-Bromo-2-isopropyl-8-methoxyphenanthridin-6-amine

A mixture of5-methoxy-2-(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-yl)benzo-nitrile(57.41 g, 0.22 mol, 1 equiv), 2,6-dibromo-4-iso-propylaniline (64.92 g,0.22 mol, 1 equiv) and potassium phosphate (153.1 g, 0.66 mol, 3 equiv)in a 4:1 mixture of toluene and water (1250 mL) was sparged withnitrogen for 1 hour. trans-Pd(PPh₃)₂Cl₂ (7.8 g, 11 mmol, 0.05 equiv) wasadded and the reaction mixture was refluxed for 20 hours. Additionalpotassium phosphate (77 g, 0.33 mol, 1.5 equiv) and trans-Pd(PPh₃)₂Cl₂(1 g, 1.43 mmol, 0.0065 equiv) were added and the reaction mixture wasrefluxed for an additional 3 hours. The layers were separated and theorganic layer was washed with hot water (2×400 mL). The organic layerwas dried over sodium sulfate and concentrated under reduced pressure.The resulting solid was triturated sequentially with dichloromethane andheptanes. Column chromatography gave the desired product (30 g).

D. Synthesis of6-Isopropyl-10-((9-(4-isopropylpyridin-2-yl)-9H-carbazol-2-yl)oxy)-3,4dihydro-dibenzo[b,ij]imidazo[2,1,5-de]quinolizine

A suspension of 4-bromo-2-isopropyl-8-methoxyphenanthridin-6-amine (8.9g, 25.8 mmol, 1 equiv), p-toluenesulfonic acid monohydrate (348 mg),freshly prepared 2-bromo-4-chlorobutanal (24 g, 129 mmol, 5 equiv) andiso-propanol (500 mL) was stirred at room temperature for 2.5 hours.Sodium carbonate (6.5 g, 77.4 mmol, 3 equiv) and deionized water (32 ml)were added, and the reaction mixture was refluxed for 16 hours. Aftercooling to room temperature, the volume of reaction mixture was reducedto ˜100 mL under reduced pressure. The mixture was diluted with ethylacetate (350 mL) and washed with saturated brine (200 mL). The organiclayer was dried over sodium sulfate and concentrated under reducedpressure. The crude product was purified by column chromatography toyield 8.44 g of product (76% yield).

E. Synthesis of 6-Isopropyl-10-methoxy-3,4-dihydrodibenzoimidazo[2,1,5-de]quinoli-zine

A solution of6-Isopropyl-10-((9-(4-isopropylpyridin-2-yl)-9H-carbazol-2-yl)oxy)-3,4dihydro-dibenzo[b,ij]imidazo[2,1,5-de]quinolizine(8.44 g, 19.6 mmol, 1.0 equiv) in dry THF (250 mL) was sparged withnitrogen for 30 minutes). After cooling to 0° C., 2M isopropylmagnesiumchloride (14.7 mL, 29.4 mmol, 1.5 equiv) in THF was added dropwise. Thereaction mixture was warmed up to room temperature and stirred for 16hours. The reaction was quenched with water (10 mL) and the THF wasremoved under reduced pressure. The residue was diluted with ethylacetate (400 mL) and washed with saturated brine (2×200 mL). The organiclayer was dried over sodium sulfate and the residue was purified bycolumn chromatography to give 3.6 g of product (58% yield).

F. Synthesis of6-Isopropyl-3,4-dihydrodibenzo[b,ij]imidazo[2,1,5-de]quinolizin-10-ol

Boron tribromide (5.4 mL, 56.78 mmol, 5 equiv) was added dropwise at−78° C. to a solution of6-Isopropyl-10-methoxy-3,4-dihydrodibenzo[b,ij]imidazo[2,1,5-de]quinoli-zine(3.6 g, 11.36 mmol, 1 equiv) in dichloromethane (200 mL). The reactionwas warmed to room temperature and stirred for 16 hours. The reactionmixture was carefully poured into 300 ml of ice water and the resultingsolid was filtered and washed sequentially with water (70 mL), ethylacetate (40 mL) and heptanes (40 mL) to give 3.6 g of product(quantitative yield).

G. Synthesis of 4′-Bromo-2-nitro-1,1′-biphenyl

A solution of potassium carbonate (84 g, 608 mmol, 3.0 equiv) in water(450 mL) was added to a mixture of 2-iodo-nitrobenzene (50 g, 200 mmol,1.0 equiv) and 4-bromobenzeneboronic acid (40.7 g, 202 mol, 1.0 equiv)in 1,2-dimethoxyethane (660 mL). The reaction was sparged with nitrogenfor 5.0 minutes. Tetrakis(triphenylphosphine)palladium(0) (2.32 g, 2mmol, 1 mol %) was added and the mixture was sparged with nitrogen foran additional 10 minutes. After refluxing for 16 hours, the reaction wascooled to room temperature and the layers were separated. The aqueouslayer was extracted with ethyl acetate (500 mL). The combined organicextracts were washed with saturated brine (500 mL), dried over sodiumsulfate, filtered and concentrated under reduced pressure. The residuewas dissolved in 25% ethyl acetate in heptanes (300 mL) and vacuumfiltered through a pad of silica gel (135 g). The pad was rinsed with25% ethyl acetate in heptanes (3×350 mL). The combined filtrates wereconcentrated under reduced pressure giving an orange solid. This residuewas suspended in heptanes (150 mL) and heated to 40° C. for 20 minutes.The suspension was allowed to cool to room temperature for 1.0 hour. Thesolid was collected by vacuum filtration, washed with heptanes (50 mL)and dried to give 4′-bromo-2-nitro-1,1′-biphenyl as a yellow solid(49.16 g, 88.4% yield).

H. Synthesis of 2-Bromo-9H-carbazole

Triphenylphosphine (156.3 g, 596 mmol, 2.5 equiv) was added over 5minutes to a solution 4′-bromo-2-nitro-1,1′-biphenyl (66.25 g, 238 mmol,1.0 equiv) in 1,2-dichlorobenzene (460 mL). The reaction was spargedwith nitrogen 5 minutes, then refluxed for 16 hours. The reaction wascooled to room temperature and vacuum distilled to remove most of the1,2-dichlorobenzene (450 mL). This dark residue was dissolved in ethylacetate (1.5 L) and treated with decolorizing carbon (50 g) at 50° C.for 30 minutes. After cooling, the mixture was filtered through Celite(200 g), then washed with ethyl acetate washes (2×650 mL). The combinedfiltrates were concentrated under reduced pressure to a volume of ˜500mL. The solution was cooled to room temperature and after 1.5 hours, theresulting pale tan solid (triphenylphosphine oxide) was removed byfiltration and discarded. The filtrate was concentrated under reducedpressure. The residue was dissolved in methanol (600 mL) and stored atroom temperature for 16 hours. The resulting tan solid was filtered,washed with methanol (2×100 mL) and dried under vacuum at 40° C. to give2-bromo-9H-carbazole as a pale tan solid (33.5 g, 57.2% yield).

I. Synthesis of 2-Bromo-9-(4-isopropylpyridin-2-yl)-9H-carbazole

A suspension of 2-bromo-9H-carbazole (13.9 g, 56.5 mmol, 1 equiv),4-isopropyl-2-chloropyridine (15.86 g, 101.7 mmol, 1.8 equiv), L-proline(1.3 g, 11.3 mmol, 0.2 equiv), copper (1) iodide (0.95 g, 5.65 mmol, 0.1equiv), potassium carbonate (19.48 g, 141.25 mmol, 2.5 equiv) and DMSO(80 mL) was sparged with nitrogen for 5 minutes. The mixture was heatedat 95° C. for 16 hours. Additional 4-isopropyl-2-chloropyridine (1.58 g,10.12 mmol, 0.18 equiv) was added, the reaction mixture was heated at155° C. for an additional 24 hours. The reaction mixture was cooled toroom temperature, diluted with ethyl acetate (750 mL), and vacuumfiltered through celite (70 g). The celite pad was washed with ethylacetate washes (2×100 mL). The combined filtrates were washed withsaturated brine (3×500 mL), dried over sodium sulfate, filtered andconcentrated under reduced pressure. This residue was purified by columnchromatography to give 1.8 g of product as a brown oil (8.6% yield).

J. Synthesis of6-Isopropyl-10-((9-(4-isopropylpyridin-2-yl)-9H-carbazol-2-yl)oxy)-3,4-dihydrodibenzo[b,ij]imidazo[2,1,5-de]quinolizine

A mixture of6-Isopropyl-3,4-dihydrodibenzo[b,ij]imidazo[2,1,5-de]quinolizin-10-ol(1.5 g, 4.93 mmol, 1 equiv),2-Bromo-9-(4-isopropylpyridin-2-yl)-9H-carbazole (1.8 g, 4.93 mmol, 1equiv), potassium phosphate (5.68 g, 24.65 mmol, 5 equiv), copper(I)iodide (0.47 g, 2.47 mmol, 0.5 equiv), picolinic acid (1.52 g, 12.33mmol, 2.5 equiv) and DMSO (150 mL) was heated at 150° C. for 4.5 hours.After cooling to room temperature, the reaction mixture was poured intowater (700 mL) and extracted with ethyl acetate (4×150 mL). The combinedorganic layers were dried over sodium sulfate and concentrated in underreduced pressure. The crude product was purified by columnchromatography to yield product as a tan solid, 1.25 g (43% yield).

K. Synthesis of platinum(II) complex of6-isopropyl-10-((9-(4-isopropylpyridin-2-yl)-9H-carbazol-2-yl)oxy)-3,4-dihydrodibenzo[b,ij]imidazo[2,1,5-de]quinolizine

6-Isopropyl-10-((9-(4-isopropylpyridin-2-yl)-9H-carbazol-2-yl)oxy)-3,4-dihydrodibenzo[b,ij]imidazo[2,1,5-de]quinolizine(400 mg, 0.68 mmol, 1 equiv) was dissolved in 60 ml of glacial aceticacid and sparged with nitrogen for 30 minutes. Then K₂PtCl₄ (283 mg,0.68 mmol, 1 equiv) was added, and the reaction mixture was refluxed for40 hours. After cooling to room temperature, the orange precipitate wasfiltered and washed sequentially with water (3×15 mL) and heptanes (10ml×2 times). The crude product (340 mg) was dissolved in 10 ml ofdichloromethane and filtered through a plug of silica gel to removeresidual K₂PtCl₄, eluting with additional dichloromethane (10 mL). Thefiltrate was reduced to half its volume and diluted with heptanes (10mL). The product was filtered and triturated with a 10% solution ofdichloromethane in heptanes (10 mL) to give product as a light yellowsolid (140 mg, 26% yield). Additional product was isolated from theacetic acid and dichloromethane/heptane filtrates.

Example 4: Synthesis of (3-phenyl-1H-pyrazole)₂Ir(MeOH)₂(OTf)

A. Synthesis of (3-phenyl-1H-pyrazole)₂IrCl₂ dimer

Iridium chloride hydrate (6.00 g, 17.02 mmol) and 1-phenyl-1H-pyrazole(5.89 g, 40.9 mmol) were combined in 2-ethoxyethanol (120 ml) and water(40 ml). The reaction mixture was heated to reflux for 16 hours undernitrogen. The resulting solid was filtered off and washed with methanoland dried to yield 8.3 g of the iridium dimer.

The iridium dimer of Example 4A (8.3 g, 8.07 mmol) was dissolved in 100mL of DCM and a solution of silver triflate (4.36 g, 16.96 mmol) in 20mL of methanol was added. The reaction mixture was stirred at roomtemperature under nitrogen for 1 hour. The mixture was filtered throughcelite and the cake was washed with DCM. The filtrates were evaporatedto yield 10.85 g of (3-phenyl-1H-pyrazole)₂Ir(MeOH)₂(OTf) (97%).

Example 5: Exemplary Compound 35 was Prepared According to Scheme 5

A. Synthesis of imidazo[1,2-f]phenanthridine

A mixture of 2-phenyl-1H-imidazole (10.0 g, 69.3 mmol, 1 equiv),1,2-dibromobenzene (19.63 g, 83.2 mmol, 1.2 equiv), cesium carbonate(67.79 g, 208.0 mmol, 3 equiv), Xantphos (4.01 g, 6.9 mmol, 0.1 equiv)and tetrakis(triphenylphosphine)palladium (8.01 g, 6.9 mmol, 0.1 equiv)in DMF (550 mL) was sparged with a stream of nitrogen for 15 minutes.The mixture was heated at 140° C. for 24 hours, then concentrated underreduced pressure. The residue was purified by column chromatography toimidazo[1,2-f]phenanthridine (10 g, 67% yield) as pale yellow solid.

B. Synthesis of 3-Bromoimidazo[1,2-f]phenanthridine

N-bromosuccinimide (1.62 g, 9.1 mmol, 1 equiv) was added to a solutionof 15 (1.99 g, 9.1 mmol, 1 equiv) in DMF (32 mL) at 0° C. After stirringat room temperature for 18 hours, the reaction was diluted with water(300 mL) and sequentially extracted with 10% dichloromethane in methylt-butyl ether (3×500 mL), ethyl acetate (2×300 mL) and dichloromethane(400 mL). The combined organic layers were dried over sodium sulfate,filtered and concentrated under reduced pressure. The residue waspurified by column chromatography to yield3-Bromoimidazo[1,2-f]phenanthridine (1.66 g, 65% yield) as an off-whitesolid.

C. Synthesis of tert-Butyl 2-(imidazo[1,2-f]phenanthridin-3-yl)acetate

Di-μ-bromobis(tri-t-butylphosphino)dipalladium (I) (2.01 g, 2.5 mmol,0.05 equiv) was added to a solution of 16 (15.4 g, 51.8 mmol, 1 equiv)in anhydrous tetrahydrofuran (220 mL) and the solution was sparged witha stream of nitrogen for 15 minutes. 0.5M 2-tert-butoxy-2-oxoethylzincbromide in diethyl ether (155 mL, 77.7 mmol, 1.5 equiv) was added undernitrogen. The reaction was stirred at 60° C. for 16 hours. Additional0.5M 2-tert-butoxy-2-oxoethylziinc chloride solution (155 mL, 77.7 mmol,1.5 equiv) and di-μ-bromobis(tri-t-butylphosphino)-dipalladium (I) (2.01g, 2.5 mmol, 0.05 equiv) were added and the reaction was stirred at 60°C. until LC/MS analysis indicated it was complete. The reaction mixturewas concentrated under reduced pressure. The residue was dissolved indichloromethane (1 L) and filtered through a Celite pad. The filtratewas concentrated under reduced pressure. The residue was purified bycolumn chromatography to give tert-Butyl2-(imidazo[1,2-f]phenanthridin-3-yl)acetate (5 g, 30% yield) as anorange solid.

D. Synthesis of Methyl 2-(imidazo[1,2-f]phenanthridin-3-yl)acetatehydrochloride

A solution of 17 (2.8 g, 8.4 mmol, 1 equiv) in 1.25M HCl (55 mL, 68.7mmol, 6.5 equiv) in methanol was stirred at 60° C. for 16 hours. Thereaction mixture was concentrated under reduced pressure. The residuewas washed with diethyl ether and dried under vacuum for 16 hours at 40°C. to give methyl 2-(imidazo[1,2-f]phenanthridin-3-yl)acetatehydrochloride (2.5 g, 100% yield) as an off-white solid.

E. Synthesis of Methyl2-(imidazo[1,2-f]phenanthridin-3-yl)-2-methylpropanoate

A 60% dispersion of sodium hydride in mineral oil (2.45 g, 61.2 mmol, 5equiv) and iodomethane (2 mL, 32.1 mmol, 2.6 equiv) were sequentiallyadded to a solution of methyl2-(imidazo[1,2-f]phenanthridin-3-yl)acetate hydrochloride (4.0 g, 12.24mmol, 1 equiv) in anhydrous DMF (45 mL) at 5° C. The mixture was stirredin a cooling bath for 30 minutes, warmed to room temperature and stirredfor 6 hours. Additional iodomethane (1.2 mL, 19.2 mmol, 1.6 equiv) wasadded. The reaction was stirred at room temperature over a weekend,quenched with methanol (32 mL) and concentrated under reduced pressure.The residual oil was diluted with dichloromethane (350 mL) and washedwith water (100 mL). The aqueous layer was extracted withdichloromethane (2×100 mL). The combined organic layers were washed withsaturated ammonium chloride (100 mL), dried over sodium sulfate,filtered and concentrated under reduced pressure. The residue waspurified by column chromatography to give methyl2-(imidazo[1,2-f]phenanthridin-3-yl)-2-methylpropanoate (1.6 g, 41%yield) as an off-white solid.

F. Synthesis of 2-(Imidazo[1,2-f]phenanthridin-3-yl)-2-methylpropanoicacid

A solution of methyl2-(imidazo[1,2-f]phenanthridin-3-yl)-2-methylpropanoate (1.6 g, 5.0mmol, 1 equiv) in methanol (100 mL) was treated with aqueous 1N sodiumhydroxide (30 mL, 30 mmol, 6 equiv) and further diluted with water (100mL). After refluxing for 5 days, the reaction was concentrated underreduced pressure. The residue was dissolved in water (100 mL) andacidified with conc. HCl to pH 5-6. The resulting white suspension wasextracted with 1 to 2 mixture of isopropanol and dichloro-methane (4×200mL). The combined organic layers were dried over sodium sulfate,filtered, concentrated under reduced pressure. The residue was driedunder high vacuum at 40° C. for 16 hours to give2-(Imidazo[1,2-f]phenanthridin-3-yl)-2-methylpropanoic acid (1.3 g, 82%yield) as white solid.

G. Synthesis of 2-(Imidazo[1,2-f]phenanthridin-3-yl)-2-methylpropanoylchloride

Thionyl chloride (1 mL, 13.7 mmol, 2 equiv) and anhydrous DMF (0.05 mL,0.6 mmol, 0.11 equiv) were added to a suspension of2-(Imidazo[1,2-f]phenanthridin-3-yl)-2-methylpropanoic acid (1.3 g, 4.2mmol, 1 equiv) in anhydrous dichloromethane (100 mL). After stirring atroom temperature for 16 hours, the mixture was concentrated underreduced pressure to give the2-(Imidazo[1,2-f]phenanthridin-3-yl)-2-methylpropanoyl chloride (1.37 g,100% yield) as an off-white solid.

H. Synthesis of3,3-Dimethyldibenzo[b,ij]imidazo[2,1,5-de]quinolizin-4(3H)-one

A mixture of 2-(Imidazo[1,2-f]phenanthridin-3-yl)-2-methylpropanoylchloride (1.37 g, 4.2 mmol, 1 equiv) and anhydrous aluminum chloride(6.0 g, 44.9 mmol, 10 equiv) in anhydrous dichloromethane (60 mL) wasstirred at room temperature for 6 hours. The reaction was cooled with anice-water bath, quenched with ice, diluted with saturated sodiumbicarbonate (300 mL) and extracted with dichloromethane (4×400 mL). Thecombined organic layers were dried over sodium sulfate, filtered andconcentrated under reduced pressure. The residue was purified usingcolumn chromatography to give3,3-dimethyldibenzo[b,ij]imidazo[2,1,5-de]quinolizin-4(3H)-one (1 g, 81%yield) as a white solid.

I. Synthesis of3,3-Dimethyl-3,4-dihydrodibenzo[b,ij]imidazo[2,1,5-de]quinolizin-4-ol

Sodium borohydride (0.24 g, 6.3 mmol, 2 equiv) was added in one portionto a solution of3,3-dimethyldibenzo[b,ij]imidazo[2,1,5-de]quinolizin-4(3H)-one (0.9 g,3.1 mmol, 1 equiv) in ethanol (70 mL) at 5° C. The reaction was stirredat room temperature for 1.5 hours and then quenched with acetone (2 mL).The reaction mixture was concentrated under reduced pressure. Theresidue was dissolved in methyl t-butyl ether (300 mL), washed withsaturated sodium bicarbonate (2×60 mL) and saturated brine (60 mL). Theorganic layer was dried over sodium sulfate, filtered and concentratedunder reduced pressure. The crude product was purified by columnchromatography to give3,3-Dimethyl-3,4-dihydrodibenzo[b,ij]imidazo[2,1,5-de]quinolizin-4-ol

(0.9 g, 100% yield) as a white solid.

J.o-(3,3-Dimethyl-3,4-dihydrodibenzo[b,ij]imidazo[2,1,5-de]quinolizin-4-yl)S-methylcarbonodithioate

A 60% dispersion of sodium hydride (0.48 g, 20.2 mmol, 5 equiv) inmineral oil was added to a solution of3,3-Dimethyl-3,4-dihydrodibenzo[b,ij]imidazo[2,1,5-de]quinolizin-4-ol(0.71 g, 2.46 mmol, 1 equiv) in anhydrous THF (70 mL) at 0° C. Afterstirring for 30 minutes at 5° C., a solution of imidazole (0.0168 g,0.24 mmol, 0.1 equiv) in anhydrous tetrahydrofuran (3.2 mL) was added,followed by the dropwise addition of carbon disulfide (0.89 mL, 14.8mmol, 6 equiv). The reaction was allowed to slowly warm to 12° C. over30 minutes. Iodomethane (0.92 mL, 14.7 mmol, 6 equiv) was added dropwise(exothermic) and the reaction was stirred at room temperature for 1hour. The reaction mixture was cooled to 5° C., diluted with saturatedbrine (140 mL) and extracted with dichloromethane (5×100 mL). Thecombined organic layers were dried over sodium sulfate, filtered andconcentrated under reduced pressure. The crude product was purified bycolumn chromatography to giveo-(3,3-Dimethyl-3,4-dihydrodibenzo[b,ij]imidazo[2,1,5-de]quinolizin-4-yl)S-methylcarbonodithioate (0.86 g, 93% yield) as a white solid.

K. Synthesis of3,3-Dimethyl-3,4-dihydrodibenzo[b,ij]imidazo[2,1,5-de]quinolizine

A solution ofo-(3,3-Dimethyl-3,4-dihydrodibenzo[b,ij]imidazo[2,1,5-de]quinolizin-4-yl)S-methylcarbonodithioate (0.98 g, 2.6 mmol, 1 equiv),2,2′-azabis(2-methylpropionitrile) (0.098 g, 0.6 mmol, 0.2 equiv) andtributyltin hydride (1.81 mL, 6.7 mmol, 2.6 equiv) in anhydrous toluene(70 mL) was stirred at 80° C. for 3.5 hours. After cooling to roomtemperature, the reaction mixture was concentrated under reducedpressure at 35° C. and absorbed onto silica gel (10 g). The crudematerial was purified by column chromatography to give3,3-Dimethyl-3,4-dihydrodibenzo[b,ij]imidazo[2,1,5-de]quinolizine (0.53g, 72% yield) as a white solid.

L. Synthesis of (3-chloropropyl)(methyl)sulfane

Sodium methanethiolate (6.14 g, 88 mmol) was dissolved in 150 mL ofEtOH, cooled in an ice bath, then 1-bromo-3-chloropropane (8.6 ml, 87mmol) was added. The solution was warmed to room temperature and stirredfor 2 hours. The precipitated solids were filtered and the filtratescondensed under vacuum. The residue was distilled under vacuum to yieldthe product as a colorless oil, 36%.

M. Synthesis of tris-[(3-methylthio)propyl]iridium(III)

(3-chloropropyl)(methyl)sulfane was synthesized by stirring the Grignardmade from (3-chloropropyl)(methyl)sulfane and magnesium turnings withIrCl₃(THT)₃ in THF, followed by column chromatography to yield a whitesolid, 32%.

N. Synthesis of Compound 35

tris-[(3-methylthio)propyl]iridium(III) from Example 5M (0.020 g, 0.044mmol) and3,3-Dimethyl-3,4-dihydrodibenzo[b,ij]imidazo[2,1,5-de]quinolizine fromExample 5K (0.036 g, 0.131 mmol) were combined in ethylene glycol (0.5ml), degassed by vacuum/backfill cycles, and stirred at reflux, turningyellow then black. The cooled residue was partitioned between water andDCM, the organics were dried and coated on celite. Purification bycolumn chromatography yielded 4 mg of Compound 35 as a beige solid (9%).

Example 6: Synthesis of Compound 48 was Carried Out as in Scheme 6

(3-phenyl-1H-pyrazole)₂Ir(MeOH)₂(OTf) from Example 4 (0.031 g, 0.045mmol) and3,3-Dimethyl-3,4-dihydrodibenzo[b,ij]imidazo[2,1,5-de]quinolizine fromExample 5K (0.024 g, 0.090 mmol) were combined in 2-ethoxyethanol (0.5ml), vacuum/backfill quickly three times, then heated at reflux undernitrogen for 2 hours. The reaction mixture was dissolved in DCM, coatedon celite, and purified by column chromatography to yield Compound 35 asa nearly colorless residue, 6 mg (18%).

Example 7: Synthesis of Compound 49 was Carried Out According to Scheme7 Below

A. Synthesis of 1-Methylphenanthridin-6-amine

A mixture of 2-bromo-3-methylaniline (38.8 g, 208 mmol, 1 equiv),(chloro(2-dicyclohexylphosphino-2′,6′-dimethoxy-1,1′-biphenyl)[2-(2′-amino-1,1′-biphenyl)]palladium(II)(2.99 g, 4.16 mmol, 0.02 equiv),2-dicyclohexyl-phosphino-2′,6′-dimethoxybiphenyl (1.71 g, 4.16 mmol,0.02 equiv) in THF (832 mL) was sparged with nitrogen for 15 minutes.(2-Cyanophenyl)zinc bromide solution (500 mL, 0.5 M in THF, 250 mmol,1.2 equiv) was added to the mixture and the reaction was refluxed for 16hours. After cooling to room temperature, the reaction was diluted withsaturated brine (10 mL) and concentrated under reduced pressure. Thesolids were dissolved in 10% methanol in dichloromethane (500 mL) and24% wt. aqueous sodium hydroxide (500 mL). The layers were separated andthe aqueous was extracted with dichloromethane (3×500 mL). The combinedorganic layers were dried over sodium sulfate, and concentrated underreduced pressure. The brown solid was sequentially triturated with 25%MTBE in heptanes (1.5 L) and dichloromethane (5×25 mL) to give 26 (10.7g, 25% yield, >95% purity) as a pale yellow solid.

B. Synthesis of 8-Methylimidazo[1,2-f]phenanthridine

A mixture of 1-methylphenanthridin-6-amine (10.7 g, 51 mmol, 1 equiv),50% wt chloroacetaldehyde in water (16 mL, 102 mmol, 2 equiv), sodiumcarbonate (13.5 g, 128 mmol, 2.5 equiv) in isopropanol (340 mL) wasrefluxed for 2 hours. The reaction was cooled to 4° C. and diluted withdichloromethane (250 mL) and saturated sodium bicarbonate (500 mL). Thelayers were separated and the aqueous layer was extracted withdichloromethane (3×250 mL). The combined organics layers were dried oversodium sulfate, and concentrated under reduced pressure to give crude8-methylimidazo[1,2-f]phenanthridine (23.8 g) as a brown solid, whichwas used subsequently.

C. Synthesis of 3-Bromo-8-methylimidazo[1,2-f]phenanthridine

A mixture of crude 8-methylimidazo[1,2-f]phenanthridine (23.8 g),N-bromosuccinimide (9.1 g, 51 mmol, 1 equiv) in dichloromethane (306 mL)was stirred at room temperature for 2 hours. Water (500 mL) was addedand the layers were separated. The aqueous was extracted withdichloromethane (3×500 mL). The combined organic layers were dried oversodium sulfate and concentrated under reduced pressure. The solids werepre-absorbed onto silica gel and purified by column chromatography togive 3-bromo-8-methylimidazo[1,2-f]phenanthridine (12 g, 98% purity) asa light brown solid.

D. Synthesis of8-Methyl-3-(2-methylprop-1-en-1-yl)imidazo[1,2-f]phenanthridine

A mixture of 3-bromo-8-methylimidazo[1,2-f]phenanthridine (12 g, 38.5mmol, 1 equiv),4,4,5,5-tetramethyl-2-(2-methylprop-1-en-1-yl)-1,3,2-dioxaborolane (10.5g, 58 mmol, 1.5 equiv), and potassium carbonate (16 g, 115.5 mmol, 3equiv) in a 5 to 1 mixture of 1,4-dioxane and water (185 mL) was spargedwith nitrogen for 15 minutes.(Chloro(2-dicyclohexylphosphino-2′,6′-dimethoxy-1,1′-biphenyl)[2-(2′-amino-1,1′-biphenyl)]palladium(II)(4.16 g, 5.78 mmol, 0.15 equiv) and2-dicyclohexylphosphino-2′,6′-dimethoxybiphenyl (2.38 g, 5.78 mmol, 0.15equiv) were added and the reaction was refluxed for 36 hours. Aftercooling to room temperature, the reaction was diluted with water (200mL). The layers were separated and the aqueous was extracted with ethylacetate (3×200 mL). The combined organics layers were dried over sodiumsulfate and concentrated under reduced pressure. The crude solid waspurified by column chromatography to give8-methyl-3-(2-methylprop-1-en-1-yl)imidazo[1,2-f]phenanthridine (8.5 g,70% yield, 90% purity) as a light brown solid.

E. Synthesis of4,4,7-Trimethyl-3,4-dihydrodibenzo[b,ij]imidazo[2,1,5-de]quinolizine

A mixture of8-methyl-3-(2-methylprop-1-en-1-yl)imidazo[1,2-f]phenanthridine (1.6 g,5.69 mmol, 1 equiv) and anhydrous aluminum chloride (3.8 g, 28.4 mmol, 5equiv) in dichloromethane (57 mL) were stirred at room temperature for16 hours. The reaction was cooled in an ice bath and water (10 mL) wasadded dropwise. The layers were separated and the aqueous layer wasextracted with dichloromethane (3×50 mL). The combined organic layerswere dried over sodium sulfate and concentrated under reduced pressure.The crude solids purified by column chromatography to give4,4,7-Trimethyl-3,4-dihydrodibenzo[b,ij]imidazo[2,1,5-de]quinolizine(1.43 g, 88% yield, 98% purity) as a light yellow solid.

F. Synthesis of2-Bromo-4,4,7-trimethyl-3,4-dihydrodibenzo[b,ij]imidazo[2,1,5-de]quinolizine

A mixture of4,4,7-Trimethyl-3,4-dihydrodibenzo[b,ij]imidazo[2,1,5-de]quinolizine(500 mg, 1.75 mmol, 1 equiv) and N-bromosuccinimide (311 mg, 1.75 mmol,1 equiv) in dichloromethane (11 mL) was stirred at room temperature for2 hours. The reaction was diluted with water (20 mL) and dichloromethane(10 mL). The layers were separated and the aqueous were extracted withdichloromethane (3×20 mL). The combined organic layers were dried oversodium sulfate and concentrated under reduced pressure. The residue waspurified by column chromatography to give2-bromo-4,4,7-trimethyl-3,4-dihydrodibenzo[b,ij]imidazo[2,1,5-de]quinolizine(575 mg, 90% yield, 97% purity) as a light brown solid.

G. Synthesis of2,4,4,7-Tetramethyl-3,4-dihydrodibenzo[b,ij]imidazo[2,1,5-de]quinolizine

A mixture of2-bromo-4,4,7-trimethyl-3,4-dihydrodibenzo[b,ij]imidazo[2,1,5-de]quinolizine(265 mg, 0.73 mmol, 1 equiv), trimethylboroxine (0.6 mL, 4.4 mmol, 6equiv) and potassium carbonate (608 mg, 4.4 mmol, 6 equiv) in a 10 to 1mixture of 1,4-dioxane and water (7 mL) was sparged with nitrogen for 15minutes.(Chloro(2dicyclo-hexylphosphino-2′,6′-dimethoxy-1,1′-biphenyl)[2-(2′-amino-1,1′-biphenyl)]palladium(II)(108 mg, 0.15 mmol, 0.2 equiv) and2-dicyclohexylphosphino-2′,6′-dimethoxybiphenyl (62 mg, 0.15 mmol, 0.2equiv) were added and the reaction was refluxed for 16 hours. Aftercooling to room temperature, the reaction was diluted with water (10 mL)and ethyl acetate (10 mL). The layers were separated and the aqueouswere extracted with ethyl acetate (3×20 mL). The combined organic layerswere dried over sodium sulfate and concentrated under reduced pressure.The residue was purified by column chromatography to give2,4,4,7-Tetramethyl-3,4-dihydrodibenzo[b,ij]imidazo[2,1,5-de]quinolizine(100 mg, 46% yield, 95% purity) as a pale yellow solid.

H. Synthesis of Compound 49

Compound 49 was synthesized in an analogous way to Compound 35, yielding13 mg of yellow powder (15%).

Example 8: Synthesis of Compound 50 was Carried Out According to Scheme8 Below

A. Synthesis of 1-chlorophenanthridin-6-amine

A mixture of 3-chloro-2-iodoaniline (8.77 g, 34.6 mmol), CyJohnPhos(0.462 g, 1.319 mmol), and Pd(CH₃CN)₂Cl₂ (0.171 g, 0.659 mmol) wasdissolved in dioxane (80 ml). Triethylamine (13.78 ml, 99 mmol) and4,4,5,5-tetramethyl-1,3,2-dioxaborolane (10.04 ml, 69.2 mmol) were addedto the solution in sequence via syringe. The reaction was reflux for 4h. The reaction was cooled to room temperature and a solid mixture of2-bromobenzonitrile (6 g, 33.0 mmol), S-Phos Pd G2 (0.475 g, 0.659mmol), S-Phos (0.271 g, 0.659 mmol), and potassium carbonate (9.11 g,65.9 mmol) was added to the reaction mixture followed by dioxane (20 ml)and water (20 ml) and the reaction was heated to 85° C. for 16 hours.The crude product was extracted with DCM and vacuumed down to yield anorange oil. This was dissolved in THF (80 mL) and sodium hydride (1.978g, 49.4 mmol) was added at 0° C. and stirred for 20 min. The reactionwas quenched with brine and extracted with DCM. Evaporation of thereaction mixture followed by trituration with ether yielded1-chlorophenanthridin-6-amine as an off-white solid (52% yield).

B. Synthesis of 8-chloroimidazo[1,2-f]phenanthridine

1-chlorophenanthridin-6-amine (864 mg, 3.78 mmol), 2-chloroacetaldehyde(50 wt % in water, 1.02 mL, 7.56 mmol), and sodium bicarbonate (635 mg,7.56 mmol) were combined in iPrOH and refluxed for 1 h. The mixture wascooled to room temperature and poured into water and filtered (99%yield).

C. Synthesis of 8-phenylimidazo[1,2-f]phenanthridine

A mixture of 8-chloroimidazo[1,2-f]phenanthridine (955 mg, 3.78 mmol),phenylboronic acid (829 mg, 6.80 mmol), S-Phos Pd G2 (109 mg, 0.151mmol), S-Phos (62.1 mg, 0.151 mmol), and potassium carbonate (522 mg,3.78 mmol) was vacuumed and back-filled with nitrogen several times.Dioxane (20 ml) and water (4 ml) were added and refluxed for 1 h. Thecrude product was extracted with DCM and brine and purified by columnchromatography to yield product (99% yield).

D. Synthesis of 3-bromo-8-phenylimidazo[1,2-f]phenanthridine

8-phenylimidazo[1,2-f]phenanthridine (1.15 mg, 3.91 mmol) and NBS (0.765g, 4.30 mmol) were combined in DMF and stirred at room temperature for30 minutes, followed by quenching with water. The resultant solid wasfiltered and dried in vacuum, yielding3-bromo-8-phenylimidazo[1,2-f]phenanthridine in 75% yield.

E. Synthesis of3-(2-methylprop-1-en-1-yl)-8-phenylimidazo[1,2-f]phenanthridine

A mixture of 3-bromo-8-phenylimidazo[1,2-f]phenanthridine (980 mg, 2.63mmol), SPhos Pd G2 (76 mg, 0.105 mmol), SPhos (43.1 mg, 0.105 mmol), andpotassium carbonate (363 mg, 2.63 mmol) was vacuumed and back-filledwith nitrogen several times. Toluene (15 ml), Water (3 ml), and4,4,5,5-tetramethyl-2-(2-methylprop-1-en-1-yl)-1,3,2-dioxaborolane(1.077 ml, 5.25 mmol) were added and heated at reflux for 16 hours. Theproduct was extracted with DCM and brine and purified by columnchromatography to give3-(2-methylprop-1-en-1-yl)-8-phenylimidazo[1,2-f]phenanthridine in 20%yield.

F. Synthesis of4,4-dimethyl-7-phenyl-3,4-dihydrodibenzo[b,ij]imidazo[2,1,5-de]quinolizine

3-(2-methylprop-1-en-1-yl)-8-phenylimidazo[1,2-f]phenanthridine (160 mg,0.459 mmol) was dissolved in DCM (10 ml) and aluminum trichloride (184mg, 1.378 mmol) was added. The reaction was stirred for 40 min at roomtemperature. The mixture was quenched with KOH(aq)/brine and extractedseveral times with DCM. The product was purified by columnchromatography to give4,4-dimethyl-7-phenyl-3,4-dihydrodibenzo[b,ij]imidazo[2,1,5-de]quinolizinein 63% yield.

G. Synthesis of Compound 50

(3-phenyl-1H-pyrazole)₂Ir(MeOH)₂(OTf) from Example 4 (0.03 g, 0.043mmol) and4,4-dimethyl-7-phenyl-3,4-dihydrodibenzo[b,ij]imidazo[2,1,5-de]quinolizine(0.030 g, 0.087 mmol) were combined in 2-ethoxyethanol (0.5 ml),vacuum/backfilled quickly three times with nitrogen, then heated atreflux under nitrogen for 2 h. The product was purified by columnchromatography to give Compound 50 in 56% yield.

Example 9: Synthesis of Compound 108 was Carried Out According to Scheme8 Below

A. Synthesis of tert-Butyl (4-((triisopropylsilyl)oxy)phenyl)carbamate

Triisopropylchlorosilane (32 mL, 0.15 mol, 1.2 equiv) and triethylamine(21 mL, 0.15 mol, 1.2 equiv) were sequentially added to a solution oftert-butyl (4-hydroxyphenyl)carbamate (26.1 g, 0.125 mol, 1 equiv) inTHF (200 mL). The reaction mixture was stirred for 16 hours at roomtemperature. The reaction was filtered and the solids were washed withTHF (2×30 mL). The combined filtrates were concentrated under reducedpressure. The crude product was purified by column chromatography togive tert-Butyl (4-((triisopropylsilyl)oxy)phenyl)carbamate (39.66 g,87% yield) as yellow oil.

B. Synthesis of 4-((Triisopropylsilyl)oxy)aniline

Trifluoroacetic acid (41.51 mL, 0.54 mol, 5 equiv) was added at roomtemperature to a solution of tert-Butyl(4-((triisopropylsilyl)oxy)phenyl)carbamate (39.66 g, 0.1085 mol, 1equiv) in dichloromethane (400 mL). After stirring for 16 hours thesolvent was removed under reduced pressure. The residue was azeotropedwith toluene (3×50 mL). The crude product was purified over silica togive 4-((Triisopropylsilyl)oxy)aniline (25 g, 87% yield).

C. Synthesis of 2,6-Dibromo-4-((triisopropylsilyl)oxy)aniline

Bromine (8.2 mL, 0.16 mol, 2.5 equiv) was added dropwise at 0° C. to asolution of 4-((Triisopropylsilyl)oxy)aniline (17 g, 64.4 mmol, 1 equiv)in a 1:1 mixture of dichloromethane and methanol (60 mL). The reactionmixture was allowed to warm up to room temperature and stirred for 16hours. The reaction mixture was diluted with dichloromethane (200 mL)and washed sequentially with 1M NaOH (2×100 mL) and saturated brine(2×100 mL). The organic layer was dried over sodium sulfate andconcentrated under reduced pressure to give2,6-Dibromo-4-((triisopropylsilyl)oxy)aniline (26.37 g, 97% yield) as abrown oil, which was used subsequently.

D. Synthesis of4-Bromo-8-methoxy-2-((triisopropylsilyl)oxy)phenanthridin-6-amine

A mixture of5-methoxy-2-(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-yl)benzonitrile(16.14 g, 62.3 mmol, 1 equiv), 51 (26.37 g, 62.3 mmol, 1 equiv) andpotassium phosphate (43.04 g, 0.187 mol, 3 equiv) in a 4 to 1 mixture oftoluene and water (500 mL) was sparged with nitrogen for 1 hour.trans-Pd(PPh₃)₂Cl₂ (2.8 g, 3.11 mmol, 0.05 equiv) was added and thereaction mixture was refluxed for 20 hours. Additional5-methoxy-2-(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-yl)benzonitrile(2.2 g, 8.5 mmol, 0.14 equiv) and trans-Pd(PPh₃)₂Cl₂ (0.3 g, 0.43 mmol,0.0069 equiv) were added and the reaction mixture was refluxed for anadditional 4 hours. The layers were separated and the organic layer waswashed with hot water (2×200 mL). The organic layer was dried oversodium sulfate and concentrated under reduced pressure. The residue waspurified by column chromatography to yield4-bromo-8-methoxy-2-((triisopropylsilyl)oxy)phenanthridin-6-amine in 20%yield.

E. Synthesis of5-Bromo-3-(2-chloroethyl)-11-methoxy-7-((triisopropylsilyl)oxy)imidazo[1,2-f]phenanthridine

A suspension of4-bromo-8-methoxy-2-((triisopropylsilyl)oxy)phenanthridin-6-amine (5.95g, 12.53 mmol, 1 equiv), p-toluenesulfonic acid monohydrate (175 mg) andfresh prepared 2 (6.67 g, 62.63 mmol, 5 equiv) in i-propanol (500 mL)was stirred at the room temperature for 2 hours. Sodium carbonate (3.25g, 37.6 mmol, 3 equiv) and deionized water (12 ml) were added and thereaction mixture was refluxed for 16 hours. After cooling to roomtemperature, the volume of reaction mixture was reduced to ˜60 ml underreduced pressure. The mixture was diluted with ethyl acetate (300 mL)and washed with saturated brine (200 mL). The organic layer was driedover sodium sulfate and concentrated under reduced pressure. The crudeproduct was purified by column chromatography to give5-bromo-3-(2-chloroethyl)-11-methoxy-7-((triisopropylsilyl)oxy)imidazo[1,2-f]phenanthridine(5.53 g, 79% yield).

F. Synthesis of10-Methoxy-6-((triisopropylsilyl)oxy)-3,4-dihydrodibenzo[b,ij]imidazo[2,1,5-de]quinolizine

A solution of5-bromo-3-(2-chloroethyl)-11-methoxy-7-((triisopropylsilyl)oxy)imidazo[1,2-f]phenanthridine(5.53 g, 9.84 mmol, 1.0 equiv) in dry THF (300 mL) was sparged withnitrogen for 30 minutes. After cooling to 0° C., 2M isopropylmagnesiumchloride in THF (7.4 mL, 14.76 mmol, 1.5 equiv) was added dropwise viasyringe. The reaction mixture was warmed to the room temperature andstirred for 16 hours. The reaction was quenched with water (10 mL) andthe THF was removed under reduced pressure. The residue was extractedwith dichloromethane (500 mL). The organic layer was washed with water(2×200 mL), dried over sodium sulfate and concentrated under reducedpressure. The crude product was purified by column chromatography togive10-methoxy-6-((triisopropylsilyl)oxy)-3,4-dihydrodibenzo[b,ij]imidazo[2,1,5-de]quinolizine(3 g, 68% yield).

G. Synthesis of10-Methoxy-3,4-dihydrodibenzo[b,ij]imidazo[2,1,5-de]quinolizin-6-ol

Tetrabutylammonium fluoride trihydrate in THF (30 mL) was added dropwiseto a solution of10-methoxy-6-((triisopropylsilyl)oxy)-3,4-dihydrodibenzo[b,ij]imidazo[2,1,5-de]quinolizine(3 g, 6.72 mmol, 1 equiv) in THF (100 mL). After stirring at roomtemperature for 16 hours, the solvent was removed under reduced pressureand the residue was extracted with dichloromethane. (80 mL). The organiclayer was washed with saturated brine (2×100 mL). Upon washing withsaturated brine, a large precipitate started to form in the organiclayer. The precipitation was filtered and washed with heptanes (2×10 mL)to give pure10-methoxy-3,4-dihydrodibenzo[b,ij]imidazo[2,1,5-de]quinolizin-6-ol(1.83 g, 94% yield).

H. Synthesis of10-Methoxy-3,4-dihydrodibenzo[b,ij]imidazo[2,1,5-de]quinolizin-6-yltrifluoromethanesulfonate

Trifluoroacetic anhydride (1.14 mL, 6.77 mmol, 1.1 equiv) and pyridine(0.744 mL, 9.24 mmol, 1.5 equiv) were sequentially added at 0° C. to amixture of10-methoxy-3,4-dihydrodibenzo[b,ij]imidazo[2,1,5-de]quinolizin-6-ol(1.79 g, 6.16 mmol, 1 equiv) in dichloromethane (100 mL). After stirringfor 15 minutes, the reaction was warm to room temperature and stirredfor 6 hours. The reaction mixture was diluted with dichloromethane (200mL) and washed with water (3×100 mL). The organic layer was dried oversodium sulfate and solvent was removed under reduced pressure. Theresidue was triturated with a 10 to 1 mixture of heptanes anddichloromethane (10 mL) to give10-methoxy-3,4-dihydrodibenzo[b,ij]imidazo[2,1,5-de]quinolizin-6-yltrifluoromethanesulfonate (2.17 g, 83% yield).

I. Synthesis of10-Methoxy-6-phenyl-3,4-dihydrodibenzo[b,ij]imidazo[2,1,5-de]quinolizine

A mixture of10-methoxy-3,4-dihydrodibenzo[b,ij]imidazo[2,1,5-de]quinolizin-6-yltrifluoromethanesulfonate (0.65 g, 1.54 mmol, 1 equiv), phenylboronicacid (0.188 g, 1.54 mmol, 1 equiv) and potassium phosphate (1.06 g, 4.62mmol, 3 equiv) in a 3:1:1 mixture of toluene:1,4-dioxane:water (500 mL)was sparged with nitrogen for 1 hour. Trans-Pd(PPh₃)₂Cl₂ (54 mg, 0.077mmol, 0.05 equiv) was added and the reaction mixture was refluxed for 16hours. The reaction mixture was diluted with dichloromethane (200 mL).The organic layer was washed with warm water (2×100 mL), dried oversodium sulfate and concentrated under reduced pressure to give10-methoxy-6-phenyl-3,4-dihydrodibenzo[b,ij]imidazo[2,1,5-de]quinolizine(0.527 g, 97% yield).

J. Synthesis of6-Phenyl-3,4-dihydrodibenzo[b,ij]imidazo[2,1,5-de]quinolizin-10-ol

1M Boron tribromide in dichloromethane (7.5 mL, 7.5 mmol, 5 equiv) wasadded dropwise at −78° C. to a solution of10-methoxy-6-phenyl-3,4-dihydrodibenzo[b,ij]imidazo[2,1,5-de]quinolizine(0.527 g, 1.5 mmol, 1 equiv) in dichloromethane (100 mL). The reactionwarmed to the room temperature and stirred for 16 hours. The reactionmixture was carefully poured in ice water (150 mL) and the resultingsolid was filtered and washed sequentially with water (30 ml) andheptanes (10 mL) to give6-phenyl-3,4-dihydrodibenzo[b,ij]imidazo[2,1,5-de]quinolizin-10-ol (0.47g, 93% yield).

K. Synthesis of10-((9-(4-Isopropylpyridin-2-yl)-9H-carbazol-2-yl)oxy)-6-phenyl-3,4-dihydro-dibenzo[b,ij]imidazo[2,1,5-de]quinolizine

A mixture of 2-Bromo-9-(4-isopropylpyridin-2-yl)-9H-carbazole (0.528 g,1.446 mmol, 1 equiv),6-phenyl-3,4-dihydrodibenzo[b,ij]imidazo[2,1,5-de]quinolizin-10-ol(0.486 g, 1.446 mmol, 1 equiv), potassium phosphate (1.67 g, 7.23 mmol,5 equiv), copper (I) iodide (0.138 g, 0.723 mmol, 0.5 equiv), andpicolinic acid (0.445 g, 3.62 mmol, 2.5 equiv) in DMSO (50 mL) washeated at 150° C. for 4.5 hours. After cooling to room temperature, thereaction mixture was poured into water (300 mL) and extracted with ethylacetate (4×100 mL). The combined organic layers were dried over sodiumsulfate and concentrated under reduced pressure. The crude product waspurified by column chromatography to give10-49-(4-isopropylpyridin-2-yl)-9H-carbazol-2-yl)oxy)-6-phenyl-3,4-dihydro-dibenzo[b,ij]imidazo[2,1,5-de]quinolizineas a tan solid (0.55 g, 61% yield).

L. Synthesis of Compound 108

A solution of10-49-(4-isopropylpyridin-2-yl)-9H-carbazol-2-yl)oxy)-6-phenyl-3,4-dihydro-dibenzo[b,ij]imidazo[2,1,5-de]quinolizine(350 mg, 0.564 mmol, 1 equiv) glacial acetic acid (60 mL) was spargedwith argon for 40 minutes. K₂PtCl₄ (234 mg, 0.564 mmol, 1 equiv) wasadded and the reaction mixture was refluxed for 16 hours. After coolingto room temperature, the yellow-greenish precipitate was filtered andwashed sequentially with water (4×15 mL) and heptanes (2×10 mL) anddried under vacuum at 20° C. for 18 hours. The crude product wasdissolved in dichloromethane (500 mL) and passed through a plug ofsilica gel 10 g) to remove residual K₂PtCl₄. The solvent was removedunder reduced pressure. The residue was triturated with a 1 to 1 mixtureof dichloromethane and heptanes (20 mL), filtered and washed withdichloromethane (2×3 mL) to give Compound 108 (40 mg, yield 8.7% yield,83.2%).

Discussion:

The general structure of one embodiment of the metal-coordinatedimidazophenanthridine ligand is shown below. The bonds of interest inthe computational study are the four carbon-nitrogen (C—N) single bonds.They are labeled as C—N₁, C—N₂, C—N_(ph) for the nitrogen that has threesingle C—N bonds, and C—N_(m) for the nitrogen that is coordinated tothe metal.

Geometry optimizations of all complexes and ligands were performed inthe Gaussian 09 software package using the hybrid B3LYP functional withthe CEP-31g effective core potential basis set. All results use thismethod unless otherwise stated in the results and discussion.

Bond strengths were calculated by breaking a bond to form a diradicalspecies on the imidazophenanthridine ligand. The bond-broken diradicalspecies was calculated as a triplet state as this is normally lower inenergy than a diradical singlet and therefore the more likely productformed in a bond breaking event. Calculations were performed at theB3LYP/6-31g(d) level and thermodynamics reported for the ground statesinglet→bond broken triplet and a lowest energy triplet (excitedstate)→bond broken triplet.

Calculated TD-DFT values for the lowest triplet excited state (T1) werealso performed at the B3LYP/CEP-31g level of theory but included theCPCM continuum solvent field using THF as the solvent which has beenshown to better match experimental results.

Bond strength calculations were performed on the following compounds:

Calculated bond strengths are shown in Table 1.

TABLE 1 C—N₁ C—N_(ph) C—N₂ C—N_(m) Calc bond bond bond bond Weakest T1strength strength strength strength bond Structure (nm) (kcal/mol)(kcal/mol) (kcal/mol) (kcal/mol) (kcal/mol) Comparative compound 1

468 11.81 74.06 25.92 88.17 n/a 39.80 102.05 11.81 Comparative compound2

474 −1.54 61.26 22.00 84.79 n/a 46.85 109.64 −1.54 Comparative compound3

476 −0.55 60.08 22.34 82.96 n/a 45.18 105.80 −0.55 Comparative compound4

5.31 28.66 n/a 45.57 5.31 Compound 1

468 35.38 90.51 n/a 36.56 35.38 Comparative ligand 1

470 18.73 83.76 34.85 99.87 n/a 45.62 110.64 18.73 Compound (1-3)

472 40.35

Table 1 shows calculated bond strengths for a series of comparativeexamples and invention Compound 1. Where two numbers are seen in thesame cell, the top number represents the thermodynamic differencebetween the excited state triplet→bond broken triplet. The lower numberrepresents the ground state singlet→bond broken triplet. If there isonly one number in the cell, it represents the triplet→triplet bondstrength (T→T). For all comparative compounds 1-4, the C—N₁ bond isshown to be the weakest bond. Bond strengths are found to be weaker inthe excited triplet state compared to the ground state singlet. This isdue to the complex having the energy of the excited state available asthe starting point to the, generally, higher energy bond broken state.In some cases, as shown for comparative compound 2 and 3, the bondbroken state is lower in energy than the starting triplet state.Therefore a bond breaking event may be considered thermodynamicallyfavorable or exothermic. It is found that when aryl substitutions areadded at the C—N₁ bond carbon atom, the bond strength decreases, as seencomparing comparative compound 1 to comparative compounds 2 and 3. Thiseffect may be due to resonance stabilization of the radical species atthe bond breaking site which is stabilized by the aryl substitution.

Stabilization of the weak C—N₁ bond can be achieved by a linkingsubstitution that links the C—N₁ carbon to the carbon on the adjacentfused aryl ring as depicted by “A” in Formula (1a). This linking groupis preferably comprised of elements that provide the proper structuralgeometry to form a bridge across the two carbons of the phenanthridinering system, providing the necessary rigidity to stabilize the C—N₁ bondwhile not lowering the triplet energy of the resulting ligand andcomplex.

The effect of the stabilizing linker is shown in Table 1 for inventionCompound 1. Here the triplet C—N₁ bond strength has greatly improvedfrom 11.81 kcal/mol, for the analogous comparative Compound 1, to 35.38kcal/mol for the invention compound, an increase in theromodynmic bondstrength of >20 kcal/mol. The two carbon linking substituent preventsthe ligand from being able to obtain the appropriate relaxed geometry ofa CN₁ bond broken state. Importantly, the triplet energy is not affectedby this substitution as both invention Compound 1 and ComparativeCompound 1 both have identical triplet energies of 468 nm bycalculation.

The minimized non bond-broken and bond-broken geometries of comparativeexample 1 are shown in FIGS. 3a and 3b . It can be seen that the bondbroken geometry relaxes the ring strain of the fused ring system of theimidazophenanthridine ligand. The tethering substitution, as shown forinvention Compound 1, inhibits the relaxed bond broken geometry, therebyincreasing the thermodynamic bond strength of the C—N₁ bond.

Further experimental evidence of the weakness of the C—N₁ bond is shownby matrix assisted laser desorption ionization mass spectroscopy(MALDI-MS). MALDI-MS can be used to probe weaknesses in bonds in theexcited states of molecules. It is believed that as a measure ofphotochemical stability, MALDI-MS can simulate some of the conditionsfound inside an OLED device, where both charged and excited states arepresent. FIG. 3 shows the MALDI-MS taken in the negative mode forcomparative compound 3. The peak for the parent ion is identified at1529 amu. However the highest intensity peak is found at 1275 amu. Thismass corresponds to a fragment of comparative compound 3 where theimidazole ring has lost the mass of two carbons and the terphenylsubstitution. The structure of proposed fragment is shown in FIG. 3. Theisotopic pattern confirms this fragment contains iridium and isconsistent with the chemical formula of the proposed fragment. Furtherfragments are identified for ligand loss at 1083 amu and imidazole ringdecomposition for two ligands at 1020 amu, as shown in FIG. 4. The datasuggests that the formation of the major fragment requires the ruptureof the C—N₁ bond that is predicted to be a weak bond by calculation.

Photophysical Properties of the Compounds of the Invention

The measured photophysical properties of the invention compounds arereported in the Table 2 below. Complexes were measured at 77K and atroom temperature in 2-methyl tetrahydrofuran solvent at highly diluteconcentrations. Photoluminescent quantum yields (PLQY, Φ_(PL)) weremeasured at 1 wt % in polymethylmethacrylate (PMMA) solid state matrixor 0.4 wt % polystyrene (PS) solid state matrix using a Hamamatsu C9920system equipped with a xenon lamp, integrating sphere and a model C10027photonic multi-channel analyzer. PL transient measurements (τ) werecarried out by time correlated single photon counting method using aHoriba Jobin Yvon Fluorolog-3 integrated with an IBH datastation hubusing a 335 nm nanoLED as the excitation source.

TABLE 2 λ_(max) (nm) τ (μs) λ_(max) (nm) Φ_(PL) Φ_(PL) Compound @ 77K @77K @ 298K PMMA PS

451 5.1 461 0.05 —

440 9.5 448 0.04 —

464 2.9 467 0.62 —

— — — 0.09 —

444 7.5 448 — 0.85

448 6.7 452 — —

— — — 0.68 —

— — — — 0.87

441 18 447 0.14 —

Compound 35 was measured to have deep blue emission, with a highestenergy peak at 77 K of 451 nm, however, the PLQY for the complex is only5%. Compound 49 demonstrates how modifications to the ligand can be usedto improve PLQY. The methyl substitution on the imidazole ring has beenfound to improve the PLQY of non-ethyl bridged phenanthridine imidazoleanalogues. In addition, methyl substitution on the exterior phenyl ringis shown by calculation to affect the ligand bite angle due to thesteric influence of the methyl substituent and the proton on theadjacent aryl ring. This steric effect pushes the phenanthridineimidazole polycyclic ring system geometry closer to the geometry of anon-bridged ligand where the coordinating sites can more closely connectto the metal. This subtle change in the geometry of the ligand allowsfor a stronger interaction between the metal and neutrally coordinatednitrogen, improving the metal-nitrogen bond strength. It is believedthat a stronger metal-nitrogen bond strength can improve the emissivityof a complex by reducing metal-nitrogen bond breaking non-radiativedecay. Therefore both methyl substitutions might be responsible forenhancing the PLQY of Compound 49 compared to Compound 35. Compound 49was measured to have a PLQY of 62% in PMMA matrix, which is very closeto the PLQY value of the non-bridged analog, Comparative Compound 6,which is measured to have a PLQY of 68%. In addition, Compound 49 ismeasured to have a much shorter excited state lifetime at 77 K of 2.9microseconds, compared to an excited state lifetime of 5.1 microsecondsfor Compound 35. This further demonstrates that the methyl substituentsimproved the radiative properties of Compound 49.

Heteroleptic examples with phenylpyrazole ligands (ppz), Compound 48 andCompound 50, are measured to have deep blue emission, but low PLQY.However, the non-bridged reference compound, Comparative Compound 8, isalso measured to have a low PLQY of 14%. It is believed that the lowefficiency may be due to the weak metal-nitrogen bond of the pyrazoleligand. To further support this assumption, tris Ir(ppz)₃ has been shownin the literature to be non-emissive in room temperature solution, buthighly emissive at 77 K. The non emissivity at room temperature isattributed to a weak metal nitrogen bond.

Platinum complexes with bridged phenanthridine imidazole ligands arealso found to be highly emissive with deep blue color. Compound 105 andComparative Compound 7 are both measured to have high PLQY values of 85%and 87%, respectively, in the optically inert polystyrene matrix.Platinum complexes may not require the ligand modifications forimproving PLQY as described for the iridium analogue, Compound 49, dueto a relatively stronger platinum-nitrogen bond strength compared toiridium.

It will be appreciated by those skilled in the art that changes could bemade to the exemplary embodiments shown and described above withoutdeparting from the broad inventive concept thereof. It is understood,therefore, that this invention is not limited to the exemplaryembodiments shown and described, but it is intended to covermodifications within the spirit and scope of the present invention asdefined by the claims. For example, specific features of the exemplaryembodiments may or may not be part of the claimed invention and featuresof the disclosed embodiments may be combined. Unless specifically setforth herein, the terms “a”, “an” and “the” are not limited to oneelement but instead should be read as meaning “at least one”.

It is to be understood that at least some of the figures anddescriptions of the invention have been simplified to focus on elementsthat are relevant for a clear understanding of the invention, whileeliminating, for purposes of clarity, other elements that those ofordinary skill in the art will appreciate may also comprise a portion ofthe invention. However, because such elements are well known in the art,and because they do not necessarily facilitate a better understanding ofthe invention, a description of such elements is not provided herein.

Further, to the extent that any methods of the present invention do notrely on the particular order of steps set forth herein, the particularorder of the steps should not be construed as limitation on the claims.The claims directed to such methods should not be limited to theperformance of their steps in the order written, and one skilled in theart can readily appreciate that the steps may be varied and still remainwithin the spirit and scope of the present invention.

All references, including publications, patent applications, andpatents, cited herein are hereby incorporated by reference to the sameextent as if each reference were individually and specifically indicatedto be incorporated by reference and were set forth in its entiretyherein.

1. A compound having a structure (L_(A))_(n)ML_(m) according to Formula1:

wherein M is a metal having an atomic weight greater than 40, n has avalue of at least 1 and m+n is the maximum number of ligands that may beattached to the metal; wherein A is a linking group selected from thegroup consisting of A1thorough A222 shown below; wherein any one of thering atoms to which R^(1b) to R^(1g) are attached may be replaced with anitrogen atom, wherein when the ring atom is replaced with a nitrogenatom the corresponding R group is not present; and wherein L is asubstituted or unsubstituted cyclometallated ligand; wherein R^(1a) isselected from the group consisting of:

wherein R^(1b) is selected from the group consisting of:

wherein R^(1c) is selected from the group consisting of:

wherein R^(1d) is selected from the group consisting of:

wherein R^(1e) is selected from the group consisting of:

wherein R^(1f) is selected from the group consisting of:

wherein which R^(1g)=H; wherein the structures A1through A222 are:


2. The compound of claim 1, wherein the ligand L_(A) is one of theligands defined by L_(Ai) designated using the formulaA^(Z)-R^(1aj)—R^(1bk)—R^(1cl)—R^(1dm)—R^(1en)—R^(1fo)—R^(1g); wherein Zis an integer from 1 to 222 whereby A^(Z) represents A1through A222;wherein j is an integer from 1 to 6; and k, l, m, n and o are integersfrom 1 to 5; whereini=222((6((5((5((5((5(o−1)+n)−1)+m)−1)+l)−1)+k)−1)+j)−1)+Z.
 3. Thecompound of claim 1, wherein the compound has a triplet excited stateand wherein the linking group A stabilizes the bond between N² andC^(1b) from cleavage when the compound is in the triplet excited state.4. The compound of claim 1, wherein the compound has a peak emissivewavelength less than 500 nm.
 5. (canceled)
 6. (canceled)
 7. The compoundof claim 1, wherein the compound is selected from the group consistingof:


8. The compound of claim 1, wherein the metal is selected from the groupconsisting of Re, Ru, Os, Rh, Ir, Pd, Pt, and Au.
 9. The compound ofclaim 1, wherein the metal is selected from the group consisting of Irand Pt.
 10. The compound of claim 1, wherein the ligand L is selectedfrom the group consisting of:

wherein each X¹ to X¹³ are independently selected from the groupconsisting of carbon and nitrogen; wherein X is selected from the groupconsisting of BR′, NR′, PR′, O, S, Se, C═O, S═O, SO₂, CR′R″, SiR′R″, andGeR′R″; wherein R′ and R″ are optionally fused or joined to form a ring;wherein each R_(a), R_(b), R_(c), and R_(d) may represent from monosubstitution to the possible maximum number of substitution, or nosubstitution; wherein R′, R″, R_(a), R_(b), R_(c), and R_(d) are eachindependently selected from the group consisting of hydrogen, deuterium,halide, alkyl, cycloalkyl, heteroalkyl, arylalkyl, alkoxy, aryloxy,amino, silyl, alkenyl, cycloalkenyl, heteroalkenyl, alkynyl, aryl,heteroaryl, acyl, carbonyl, carboxylic acids, ester, nitrile,isonitrile, sulfanyl, sulfinyl, sulfonyl, phosphino, and combinationsthereof; and wherein any two adjacent substituents of R_(a), R_(b),R_(c), and R_(d) are optionally fused or joined to form a ring or form amultidentate ligand. 11.-12. (canceled)
 13. The compound of claim 1,wherein the ligand L is selected from the group consisting of:


14. The compound of claim 1, wherein ligand L is selected from the groupconsisting of:


15. The compound of claim 1, wherein the compound is (L_(A))₃Ir.
 16. Thecompound of claim 10, wherein the compound is (L_(A))Ir(L)₂ or(L_(A))₂Ir(L).
 17. The compound of claim 2, wherein the compound isCompound A-x having formula of (L_(Ai))₃Ir, Compound B-y having formulaof (L_(Ai))Ir(L_(q))₂, or Compound C-z having formula of(L_(Ai))₂Ir(L_(q)); wherein i is defined in claim 2, q is an integerfrom 1 to 254; wherein x=i, y=254(i−1)+q, z=254(i−1)+q. wherein L₁ toL₂₅₄ have the following structures:


18. The compound of claim 1, wherein the compound has a structure ofFormula 2:

wherein M is Pt; wherein A¹ and A² are linking groups, eachindependently selected from the group consisting of A1 through A222;wherein R^(2b), R^(2c), R^(2d), R^(2e), and R^(2f) are independentlyselected from the same respective groups as for R^(1b), R^(1c), R^(1d),R^(1e), and R^(1f), wherein any one of the ring atoms to which R^(1b) toR^(1f) and R^(2b) to R^(2f) are attached may be replaced with a nitrogenatom, wherein when the ring atom is replaced with a nitrogen atom thecorresponding R group is not present; and wherein R^(ab) and R^(ac)and/or R^(ga) and R^(gb) may bond to form a second linking group havingone to three linking atoms each independently selected from the groupconsisting of B, N, P, O, S, Se, C, Si, Ge or combinations thereof.19.-22. (canceled)
 23. An organic light emitting device (OLED)comprising: an anode; a cathode; and an organic layer, disposed betweenthe anode and the cathode, comprising a compound having a structure(L_(A))_(n)ML_(m) according to Formula 1:

wherein M is a metal having an atomic weight greater than 40, n has avalue of at least 1 and m+n is the maximum number of ligands that may beattached to the metal; wherein A is a linking group selected from thegroup consisting of A1thorough A222 shown below; wherein any one of thering atoms to which R^(1b) to R^(1g) are attached may be replaced with anitrogen atom, wherein when the ring atom is replaced with a nitrogenatom the corresponding R group is not present; and wherein L is asubstituted or unsubstituted cyclometallated ligand; wherein R^(1a) isselected from the group consisting of:

wherein R^(1b) is selected from the group consisting of:

wherein R^(1c) is selected from the group consisting of:

wherein R^(1d) is selected from the group consisting of:

wherein R^(1e) is selected from the group consisting of:

wherein R^(1f) is selected from the group consisting of:

wherein which R^(1g)=H; wherein the structures A1through A222 are:


24. The OLED of claim 23, wherein the organic layer is an emissive layerand the compound is an emissive dopant or a non-emissive dopant.
 25. TheOLED of claim 23, wherein the organic layer further comprises a host,wherein the host comprises at least one selected from the groupconsisting of metal complex, triphenylene, carbazole, dibenzothiophene,dibenzofuran, dibenzoselenophene, azatriphenylene, azacarbazole,aza-dibenzothiophene, aza-dibenzofuran, and aza-dibenzoselenophene. 26.The OLED of claim 23, wherein the organic layer further comprises ahost, wherein the host is selected from the group consisting of:

and combinations thereof.
 27. A consumer product comprising an organiclight-emitting device comprising: an anode; a cathode; and an organiclayer, disposed between the anode and the cathode, comprising a compoundhaving a structure (L_(A))_(n)ML_(m) according to Formula 1:

wherein M is a metal having an atomic weight greater than 40, n has avalue of at least 1 and m+n is the maximum number of ligands that may beattached to the metal; wherein A is a linking group selected from thegroup consisting of A1thorough A222 shown below; wherein any one of thering atoms to which R^(1b) to R^(1g) are attached may be replaced with anitrogen atom, wherein when the ring atom is replaced with a nitrogenatom the corresponding R group is not present; and wherein L is asubstituted or unsubstituted cyclometallated ligand; wherein R^(1a) isselected from the group consisting of:

wherein R^(1b) is selected from the group consisting of:

wherein R^(1c) is selected from the group consisting of:

wherein R^(1d) is selected from the group consisting of:

wherein R^(1e) is selected from the group consisting of:

wherein R^(1f) is selected from the group consisting of:

wherein which R^(1g)=H; wherein the structures A1through A222 are:


28. The consumer product of claim 27, wherein the consumer product isone of a flat panel display, a curved display, a computer monitor, amedical monitor, a television, a billboard, a light for interior orexterior illumination and/or signaling, a heads-up display, a fully orpartially transparent display, a flexible display, a rollable display, afoldable display, a stretchable display, a laser printer, a telephone, acell phone, tablet, a phablet, a personal digital assistant (PDA), awearable device, a laptop computer, a digital camera, a camcorder, aviewfinder, a micro-display that is less than 2 inches diagonal, a 3-Ddisplay, a virtual reality or augmented reality display, a vehicle, avideo wall comprising multiple displays tiled together, a theater orstadium screen, or a sign.